Peptide calculator
Peptide reconstitution calculator
Enter what is printed on your vial, how much bacteriostatic water you add, and the amount you want to draw. The calculator returns the concentration and the units on a U-100 insulin syringe. It does not suggest a dose for any peptide.
Arithmetic only: concentration = milligrams divided by millilitres; micrograms per unit = concentration divided by 100; units = amount divided by micrograms per unit. The tool does not know what is in your vial, whether it is what the label says, or what amount is appropriate. Doses below 2 units and hand-drawn small volumes carry measurable error (PMID 8502520, PMID 39101185).
The peptide calculator in three numbers
Three numbers explain every peptide calculator result, and two of them come from measurement rather than convention.
A 1 ml, 0.5 ml and 0.3 ml U-100 syringe all mark 100 units per millilitre, so one unit is always 0.01 ml. The barrel size only changes how many units fit and how far apart the lines are. Concentrated U-500 insulin exists precisely because the same syringe then holds five times the drug per line, which is why hospitals build separate safety processes around it (PMID 34746953).
In 198 measured draws by 33 diabetes-ward nurses, the median error was 0.6 units for 2- and 6-unit targets and 0.7 units for a 10-unit target; the largest single errors were 2.3, 4.0 and 3.3 units, and errors were significantly larger when the air bubble check was skipped (PMID 39101185). A draw of 5 units carries a built-in error of roughly a tenth.
When pediatric nurses tried to deliver 0.5, 1.0 and 2.0 units of U-100 insulin, the measured deliveries were 0.98, 1.64 and 2.15 units; 0.3 ml syringes were no better than 0.5 ml, and the authors concluded that injections under 20 microlitres, 2 units, have unacceptable error (PMID 8502520). The fix is more water, not a smaller syringe.
Every measured figure on this page is taken from a PubMed abstract, the Bacteriostatic Water for Injection USP label or a published standard, all listed at the end. The peptide calculator performs arithmetic on the numbers you enter; it recommends no amount of any peptide.
What this peptide calculator covers
Reconstitution arithmetic: milligrams in the vial, millilitres of water, concentration, micrograms per unit, units to draw, millilitres to draw and draws per vial.
Syringes: why U-100 means 100 units per millilitre on every barrel size, and what has been measured about the accuracy of small hand-drawn volumes.
Bacteriostatic water: what the USP label says it is, who it must not be used in, and what benzyl alcohol has been shown to do.
Stability after reconstitution: what has actually been measured on lyophilised peptides and proteins once water is added.
Not coveredHow much of any peptide to use, how often, or for how long. The peptide calculator has no peptide presets on purpose. The amount you type is yours; the page does not check it against anything.
What is in your vial. A research-chemical vial carries no assay. The maths assumes the label is true; nothing on this page can tell you whether it is. Peptide research vs human use explains why that matters.
Whether a peptide works or is safe. That is on the compound pages, starting with BPC-157, TB-500, CJC-1295 and ipamorelin, and on peptide side effects.
How to use the peptide reconstitution calculator
Four inputs, one result. Every input to the peptide calculator is something you can read off a label or a syringe; none of it is a decision the peptide calculator makes for you.
1. Enter the milligrams on the vial into the peptide calculator. Lyophilised peptides are sold by mass: a vial labelled 5 mg contains five milligrams of powder before any water is added. Use the chips for common vial sizes or type the figure. If the label reads in micrograms, divide by 1,000.
2. Enter the water you add. This is the only number you actually choose, and it is the one that sets everything else. More water means a weaker solution, more micrograms per unit become fewer, and the same amount becomes a longer, easier draw on the syringe. Less water means a stronger solution and a shorter draw. The vial itself does not care; it is a question of what you can measure reliably, which the two accuracy studies below answer (PMID 8502520, PMID 39101185).
3. Enter the amount you want to draw, in micrograms or milligrams. This is your figure. The peptide calculator converts it into units and shows the syringe filling to that line. It does not validate the figure against any peptide, because it has no idea which peptide it is.
4. Pick the syringe in the peptide calculator. All three options are U-100, so the units are identical; the choice only changes how many units fit and how the barrel is marked. If the result overflows the barrel, the status line says so; if it falls under 2 units, it warns that the volume is below what an insulin syringe can deliver reproducibly (PMID 8502520).
Read the peptide calculator status line before the big number. Green means the draw fits the barrel and is above the volumes where hand measurement gets unreliable; amber means it fits but is short enough that the measured error in trained hands is a meaningful fraction of the dose; red means it does not fit or exceeds the vial. Changing the water volume is the lever for all three.
The maths behind the peptide dosage calculator, with worked examples
The peptide dosage calculator on this page is a peptide reconstitution calculator in the strict sense: a concentration calculator. A worked example with round numbers shows every step. Take a vial labelled 5 mg and add 2 ml of bacteriostatic water. The concentration is 5 divided by 2, or 2.5 mg per ml. A U-100 syringe holds 100 units per millilitre, so one unit is 0.01 ml, and 2.5 mg per ml divided by 100 gives 0.025 mg, or 25 mcg, per unit. An amount of 250 mcg is therefore 250 divided by 25, which is 10 units, or 0.10 ml; the 5 mg vial holds 5,000 mcg, so it contains 20 such draws.
| Vial and water | Concentration and per unit | Amount drawn | Units on U-100 |
|---|---|---|---|
| 5 mg in 2 ml | 2.5 mg/ml; 25 mcg per unit | 250 mcg | 10 units (0.10 ml) |
| 5 mg in 1 ml | 5 mg/ml; 50 mcg per unit | 250 mcg | 5 units (0.05 ml) |
| 5 mg in 5 ml | 1 mg/ml; 10 mcg per unit | 250 mcg | 25 units (0.25 ml) |
| 10 mg in 2 ml | 5 mg/ml; 50 mcg per unit | 100 mcg | 2 units (0.02 ml), at the accuracy floor |
| 10 mg in 3 ml | 3.33 mg/ml; 33.3 mcg per unit | 1 mg | 30 units (0.30 ml) |
| 2 mg in 1 ml | 2 mg/ml; 20 mcg per unit | 2 mg | 100 units: the whole vial in one full syringe |
| 1 mg in 2 ml | 0.5 mg/ml; 5 mcg per unit | 50 mcg | 10 units (0.10 ml) |
| 15 mg in 1.5 ml | 10 mg/ml; 100 mcg per unit | 2.5 mg | 25 units (0.25 ml) |
| 20 mg in 2 ml | 10 mg/ml; 100 mcg per unit | 5 mg | 50 units (0.50 ml); 4 draws per vial |
| 50 mg in 5 ml | 10 mg/ml; 100 mcg per unit | 10 mg | 100 units: overflows a 0.5 ml or 0.3 ml syringe |
Two patterns fall out of the peptide calculator table. Doubling the water halves the micrograms per unit and doubles the units for the same amount, which is why the water volume is the only lever that matters once the vial is fixed. And amounts that come out under 2 units are not a small-syringe problem but a dilution problem: the pediatric accuracy study found 0.3 ml syringes no more accurate than 0.5 ml at those volumes (PMID 8502520), so the answer is always more water.
The amounts in the peptide calculator table are arithmetic examples chosen for round numbers. They are not amounts of any peptide, and the page does not know what would be appropriate for one.
Syringes and units: why U-100 is the whole story
The peptide calculator reports units because an insulin syringe is graduated in units, not millilitres, and the unit is a unit of insulin, not of volume. That is the root of most confusion. U-100 means the syringe is designed for insulin at 100 units per millilitre, so the 100 mark on a 1 ml syringe is exactly 1 ml, the 50 mark on a 0.5 ml syringe is 0.5 ml, and every single unit line on any of them is 0.01 ml. For a peptide the unit means nothing chemically; it is a volume line. What the line holds depends entirely on the dilution you chose, which is what the peptide calculator works out.
| Question | What the data say | Read as |
|---|---|---|
| Smallest reliable dose on an insulin syringe | Attempts at 0.5, 1.0 and 2.0 units delivered 0.98, 1.64 and 2.15 units; parents ranged from 0.64 to 1.30 for a 1-unit target; below 20 microlitres, 2 units, error was unacceptable (PMID 8502520) | Pediatric nurses and parents, gravimetric |
| Error on 2-, 6- and 10-unit draws | Median 0.6, 0.6 and 0.7 units; maximum 2.3, 4.0 and 3.3 units; larger when air bubbles were not checked; experience and time of day made no difference (PMID 39101185) | 33 nurses, 198 draws |
| Accuracy of hand-prepared syringes in general | Of 500 anaesthesia syringes analysed, 29 percent were outside plus or minus 10 percent of the intended concentration, 18 percent off by 20 percent, 8 percent by 50 percent and 4 percent by 100 percent or more; dilution steps were the source (PMID 23292267) | Spectrophotometry, anaesthesiologists |
| Why concentration changes are dangerous | U-500 insulin is five times as concentrated as U-100; a hospital built order alerts, pharmacist verification and dedicated devices because the same syringe line carries five times the drug (PMID 34746953) | Cleveland Clinic process |
| Units versus millilitres on the syringe | U-100: 100 units per ml, 1 unit = 0.01 ml on 1 ml, 0.5 ml and 0.3 ml barrels; half-unit markings exist on some 0.3 ml syringes | ISO 8537 insulin syringe standard |
The practical reading of those rows for a peptide calculator: the barrel size does not buy accuracy, dilution does; a draw under 2 units should be re-diluted rather than attempted; and the air bubble check that the nurses skipped is the single procedural step that showed up in the error data (PMID 39101185). The 29 percent figure from the anaesthesia study is worth holding in mind whenever a serial dilution is involved, because every extra dilution step is another place for the concentration to drift (PMID 23292267).
Bacteriostatic water and who must not use it
Bacteriostatic Water for Injection, USP is sterile water with 0.9 percent, 9 mg per ml, of benzyl alcohol added as a bacteriostatic preservative in the 30 ml plastic multiple-dose vial, and 1.1 percent in the 20 ml glass vial; the label indicates it only for diluting or dissolving drugs for intravenous, intramuscular or subcutaneous injection, and it is stored at 20 to 25 degrees Celsius (Bacteriostatic Water for Injection USP label). The preservative is what makes a multiple-dose vial possible: it inhibits bacterial growth between the repeated needle entries a reconstituted peptide vial gets over days or weeks. Under USP General Chapter 797, an opened multiple-dose container is assigned a beyond-use date of 28 days unless the manufacturer states otherwise.
The same preservative is why the label carries two hard limits. It states in capitals that the product is not for use in neonates, because benzyl alcohol has been associated with toxicity in that group (Bacteriostatic Water for Injection USP label); the association is the gasping syndrome described in premature infants in 1982 (PMID 7133084), and in neonatal and adult mice the median lethal dose of benzyl alcohol was about 1,000 mg per kilogram, with rapid conversion to benzaldehyde (PMID 3761172).
The label also warns that intravenous injection of bacteriostatic water without a solute may cause hemolysis, because the solution is hypotonic; it is to be used intravenously only when the additives make the mixture approximately isotonic (Bacteriostatic Water for Injection USP label).
| Point | Source | Read as |
|---|---|---|
| Composition and purpose | 0.9 percent benzyl alcohol, multiple-dose vial, for diluting or dissolving drugs for injection (Bacteriostatic Water for Injection USP label) | Label |
| Not for neonates | Stated on the label; benzyl alcohol toxicity in neonates (Bacteriostatic Water for Injection USP label); gasping syndrome (PMID 7133084) | Label limit |
| Not intravenously on its own | Hypotonic; hemolysis without a solute (Bacteriostatic Water for Injection USP label) | Label limit |
| Not for inhalation | Four of five healthy adults who nebulised bacteriostatic saline four times a day for two weeks developed bronchitis with bronchoscopic evidence (PMID 7807035) | Randomised, 10 volunteers |
| Less injection pain | Benzyl alcohol-preserved saline reduced pain of periocular botulinum toxin and anaesthetic injections across 62 studies since 1928, with minimal complications (PMID 35017698); intradermal bacteriostatic saline compared with buffered lidocaine before IV cannulation in 376 patients (PMID 23164205) | Review and randomised trial |
| Bacterial control after reconstitution | Reconstituted botulinum toxin stored refrigerated for 36 days showed no bacterial growth in either preserved or unpreserved saline (PMID 38133187); no growth in refrigerated saline-reconstituted toxin over 4 weeks (PMID 16856132) | Measured, one product class |
| Animal toxicity | Mouse median lethal dose about 1,000 mg per kg; toxicity rose when alcohol dehydrogenase was blocked (PMID 3761172) | Animal |
For the peptide calculator, sterile water for injection without preservative is the alternative, and the label difference is the whole difference: an unpreserved vial is single-use, because nothing in it stops bacteria growing after the first needle. For a vial that will be entered many times, the preservative is the point. For a single dose drawn immediately, either works. What no water does is change the arithmetic; the peptide calculator treats a millilitre as a millilitre.
How long a reconstituted peptide lasts: what has been measured
The honest answer, and the one limit a peptide calculator cannot show, is that stability after reconstitution has been measured for pharmaceutical peptides and proteins under controlled conditions, and not for research-chemical vials at all. The pharmaceutical data are still the best guide to what happens when water meets a lyophilised peptide, and they point in one direction: it depends on the peptide, the concentration and the temperature, and it is not always what the powder form would suggest.
The clearest example, and the reason a peptide calculator result has a shelf life, is teriparatide, the parathyroid hormone fragment used for osteoporosis. Its lyophilised formulations were stable for months as powder, but after reconstitution their physical stability varied considerably with concentration and storage temperature, with precipitation appearing within two to four weeks in some samples, while the same peptide never freeze-dried stayed clear in solution for twelve weeks; lyophilisation itself had made the peptide more prone to aggregate (PMID 26620825). A model study on lyophilised secretin, a peptide hormone that went into drug shortage over particulate growth, likewise traced particles to formulation and storage temperature rather than to filtration (PMID 25636302).
Proteins tell the same story with more detail, and none of it enters a peptide calculator. A reconstituted botulinum toxin product kept refrigerated at 2 to 8 degrees held its pH, biological activity and recoverable neurotoxin over 36 days in one study and 7 days in another, in preserved and unpreserved saline alike, with no bacterial growth (PMID 38133187). Yet an older toxin product reconstituted with saline and refrigerated for one, two or four weeks produced less muscle paralysis in 32 volunteers than freshly reconstituted material, again with no bacterial growth, and the authors advised against using refrigerated stored toxin (PMID 16856132). Cold storage kept it sterile; it did not necessarily keep it potent.
What follows for the peptide calculator is modest. The peptide calculator assumes the milligrams on the label are all still in solution when you draw. The pharmaceutical literature says that assumption weakens with time, concentration and warmth, and that the rate is specific to the molecule. For an unstudied peptide from an unregulated source, nothing on this page or anywhere else can put a number on it.
Five mistakes people make with a peptide calculator
Each of these produces a wrong number from correct arithmetic, because the arithmetic was fed the wrong input.
1. Reading peptide calculator units as micrograms. A unit is 0.01 ml of whatever is in the syringe. At 5 mg in 2 ml a unit holds 25 mcg; at 5 mg in 1 ml it holds 50 mcg. The same 10-unit draw is twice the peptide in the second case. The syringe never knows.
2. Confusing milligrams and micrograms in the peptide calculator. A vial is labelled in milligrams and most amounts people type are in micrograms; 1 mg is 1,000 mcg. Entering 250 with the unit set to mg asks for 250 mg from a 5 mg vial, and the status line will say so.
3. Chasing a small peptide calculator result with a smaller syringe. A 0.3 ml syringe was no more accurate than a 0.5 ml at 0.5 to 2 units (PMID 8502520). The answer to a draw under 2 units is more water in the vial, not a finer barrel.
4. Skipping the air bubble check after the peptide calculator. It was the one procedural step that correlated with error in the nurse study; experience and time of day did not (PMID 39101185).
5. Assuming the vial is what the label says. A peptide calculator cannot know. Hospital syringes prepared by anaesthesiologists were off by 10 percent or more 29 percent of the time (PMID 23292267); a research vial has no assay at all, and peptide research vs human use explains what that means in practice.
Verdict: a three-line calculation, and the parts of it that are not arithmetic
The peptide calculator answers the only question a vial and a syringe can answer between them: at this dilution, how many units hold this amount. Everything else, whether the amount is sensible, whether the powder is what it claims, and whether the solution is still intact a fortnight later, lies outside the arithmetic.
The measured parts are these: an insulin syringe cannot deliver under 2 units reliably (PMID 8502520), trained hands miss by a median of 0.6 units on small draws (PMID 39101185), a dilution step is where hand-prepared syringes go wrong (PMID 23292267), bacteriostatic water is not for neonates, inhalation or intravenous use on its own (label; PMID 7133084, PMID 7807035), and reconstituted peptides can precipitate or lose potency on a timescale of weeks that depends on the molecule (PMID 26620825, PMID 16856132).
Use the peptide calculator for the arithmetic, keep the draw above the volumes where measurement falls apart, and read the compound pages for everything the arithmetic cannot tell you. The wider context is on what are peptides and peptide side effects.
Peptide calculator: frequently asked questions
How does the peptide reconstitution calculator work?
It divides the milligrams on the vial by the millilitres of water to get a concentration in mg per ml, divides that by 100 to get the micrograms held by one unit of a U-100 insulin syringe, and divides the amount you want by that figure to get units. For 5 mg in 2 ml, one unit holds 25 mcg and 250 mcg is 10 units. It suggests no amount for any peptide.
How much bacteriostatic water do I add to a 5 mg vial?
The peptide calculator does not choose that for you, because there is no single right answer: the water only sets how long the draw is. With 1 ml each unit holds 50 mcg, with 2 ml it holds 25 mcg, with 5 ml it holds 10 mcg. The measured constraint is that draws under 2 units cannot be delivered reliably on an insulin syringe (PMID 8502520), so pick a volume that puts your amount comfortably above that.
How many units is 1 ml on an insulin syringe?
100 units on any U-100 syringe, which is why the peptide calculator works in units: regardless of whether the barrel holds 1 ml, 0.5 ml or 0.3 ml. One unit is 0.01 ml. The unit is a volume line; what it holds depends on the dilution.
What is bacteriostatic water and can I use sterile water in the peptide calculator?
Bacteriostatic Water for Injection USP is sterile water with 0.9 percent benzyl alcohol as a preservative, labelled only for diluting or dissolving drugs for injection. The preservative is what allows a multiple-dose vial to be entered repeatedly. Sterile water without preservative is single-use. The arithmetic is identical for both.
Who should not use bacteriostatic water?
The label states it is not for use in neonates because of benzyl alcohol toxicity, the gasping syndrome first described in premature infants (PMID 7133084), and warns against intravenous injection without a solute because the hypotonic solution can cause hemolysis. Nebulised bacteriostatic saline caused bronchitis in four of five healthy adults in a two-week trial (PMID 7807035).
How accurate is a peptide calculator result once drawn on an insulin syringe?
In 198 draws by 33 nurses the median error was 0.6 to 0.7 units on 2- to 10-unit targets, with maximum errors of 2.3 to 4.0 units, and errors were larger when air bubbles were not checked (PMID 39101185). Below 2 units the error becomes unacceptable and a smaller syringe does not help (PMID 8502520).
How long does a reconstituted peptide stay good after the peptide calculator?
It has been measured only for pharmaceutical products. Reconstituted teriparatide precipitated within two to four weeks in some samples depending on concentration and temperature (PMID 26620825); a reconstituted botulinum toxin held activity refrigerated for 36 days in one study (PMID 38133187) but lost potency after one to four weeks refrigerated in another (PMID 16856132). No such measurement exists for research-chemical vials.
Does the peptide dosage calculator tell me what dose to take?
No. It has no peptide presets and does not check the amount you enter against anything. The compound profiles on this site describe what has and has not been measured for each peptide; none of them gives a dose, because for most of these compounds no human dose-finding data exist.
Sources and further reading
Every measured figure on this peptide calculator page comes from one of the 16 sources below: 13 papers checked against their PubMed abstracts on 30 September 2026, the Bacteriostatic Water for Injection USP label, and two published standards, marked as such. Animal studies are cited as such and never as human results. Reference links are dofollow to support open science.
Keep reading
Four pages around the peptide calculator: what peptides are, how to read peptide research without overreaching, what the side effect record shows, and the most searched compound on this site.
Final Educational Note
This page is educational and is not medical advice. The peptide calculator performs arithmetic on numbers you enter; it recommends no amount, schedule or protocol for any peptide, does not know what your vial contains, and is not an encouragement to use research chemicals or performance-enhancing drugs, which carry serious health and legal risks. The measured facts about syringes, bacteriostatic water and reconstitution stability come from the sources listed above. More guides sit on the PED side effects hub.
Redness, swelling or pain that spreads from an injection site, fever after an injection, or any breathing difficulty are clinical findings that a physician should assess at once. Read more about how this site works on the about page and in the full disclaimer.
