Reconstitution
Peptide Reconstitution Calculator
Published by Peptara Labs · Updated · How we research and check our pages
The short answer
Peptide reconstitution calculator inputs are the vial strength and the water volume. Reconstitution math is two divisions. Concentration in mg per mL is the vial strength in mg divided by the bacteriostatic water in mL. Because a U-100 insulin syringe reads 100 units to 1 mL, one unit holds a hundredth of that concentration. Enter your own vial strength and water volume below and the calculator does both divisions and shows its working.
The volume of bacteriostatic water you add sets the concentration and nothing else. It never changes how much peptide is in the vial. That one fact is why the same vial produces completely different unit counts for different people, and why both can be right.
Education only
This calculator recommends nothing. It converts numbers you type into a concentration and a unit count, and it has no opinion about what those numbers should be. The starting values are labeled examples chosen because they divide cleanly. Nothing on this page is a dose, a protocol or medical advice, and any decision about use belongs with a qualified clinician.
The calculator
Three inputs, two outputs, and the arithmetic printed underneath so you can check it by hand.
This tool computes, it does not recommend. It converts the three numbers you type into a concentration and a unit count. It does not know what you are working with, it does not set an amount, and nothing it returns is a dose or an instruction. Any decision about use belongs with a qualified clinician.
The three fields start on example values (a 10 mg vial, 2 mL of bacteriostatic water, converting 1 mg). They are placeholders chosen because they divide cleanly. Replace them with your own figures.
Concentration
5mg/mL
10 mg spread through 2 mL of bacteriostatic water.
One unit holds
0.05mg
A U-100 barrel is 100 units to 1 mL, so one unit carries a hundredth of the concentration, or 50 mcg.
1 mg on a U-100 syringe
20units
At 5 mg/mL, 1 mg works out to 20 units. The barrel is graduated in whole units, so a figure between two ticks cannot be drawn exactly. This is arithmetic, not a dose and not an instruction.
The math it just did
concentration = vial mg / bac water mL
= 10 / 2 = 5 mg/mL
units = (amount mg / vial mg) × (bac water mL × 100)
= (1 / 10) x (2 x 100) = 20 units
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The two formulas, in full
Nothing here is specific to a compound. The same two lines cover every lyophilized vial and every volume.
Concentration
mg per mL = vial strength in mg / bac water in mL
A 10 mg vial in 2 mL is 5 mg per mL. The same 10 mg vial in 1 mL is 10 mg per mL. The vial still holds 10 mg in both cases.
Units on a U-100 syringe
units = (amount in mg / vial strength in mg) × (bac water in mL × 100)
A U-100 insulin syringe holds 100 units per 1 mL, which is where the 100 comes from. Put a 10 mg vial into 2 mL and the vial holds 200 units in total, each carrying 0.05 mg.
Two limits the arithmetic does not know about
A single 1 mL U-100 syringe holds 100 units, so any result above 100 is correct as arithmetic but is not one draw. And the vial has to physically hold the volume you plan to add. Check both before trusting a number.
Working it out by hand
Four steps, and the calculator above is doing exactly these. Being able to reproduce the number without the tool is the point: a calculator you cannot check is just another thing to trust.
Read the vial strength off the label
The label states the mass of lyophilized peptide in the vial, in mg. This number is fixed. Adding bacteriostatic water never changes it, which is the single most useful thing to understand about the arithmetic that follows.
Record the bacteriostatic water volume you actually added
The volume you add sets the concentration and nothing else. Use the volume you actually put in rather than the one you meant to, and write it on the vial, because nothing on the vial records it for you and every figure downstream depends on it.
Divide the vial strength by the volume to get the concentration
Concentration in mg per mL is the vial strength in mg divided by the bacteriostatic water in mL. A 10 mg vial in 2 mL is 5 mg per mL. A 10 mg vial in 1 mL is 10 mg per mL. Same vial, same peptide, different concentration.
Convert the concentration to units on a U-100 barrel
A U-100 insulin syringe reads 100 units to 1 mL, so one unit holds one hundredth of the concentration. At 5 mg per mL, one unit holds 0.05 mg. Working the other way, units equals the amount in mg divided by the vial strength in mg, multiplied by the bacteriostatic water in mL times 100.
This page is the math. The method is next door.
Mixing a vial correctly is a physical procedure: room temperature first, alcohol on both stoppers, the water down the inside of the glass, swirl rather than shake, refrigerate afterwards. None of that is arithmetic, so it lives on its own pages rather than being crammed in beside a calculator.
Keep reading
The method, the units, and the reports behind the vial strengths
How to reconstitute peptides
The step-by-step method behind the math, plus the catalog calculator.
Units vs mg
Why the syringe reads in units and the vial reads in mg.
Peptide injection basics
What happens after the vial is mixed.
Bacteriostatic water
What the diluent actually is, how the sizes divide, and what a bottle costs.
Peptide glossary
Plain definitions for bac water, lyophilized, diluent, and the rest.
Certificates of analysis
The published batch reports behind the vial strengths we state.
Reconstitution calculator: FAQ
How do you calculate peptide reconstitution?
Two divisions. Concentration in mg per mL is the vial strength in mg divided by the bacteriostatic water volume in mL. To express an amount in syringe units, take the amount in mg, divide it by the vial strength in mg, and multiply by the bacteriostatic water volume in mL times 100. The multiplication by 100 is there because a U-100 insulin syringe reads 100 units to 1 mL. The calculator on this page performs both divisions on whatever numbers you enter.
Does adding more bacteriostatic water change how much peptide is in the vial?
No. A 10 mg vial holds 10 mg of peptide whether you add 1 mL, 2 mL or 5 mL. The water changes the concentration, which changes how many units on the syringe correspond to a given amount in mg. It does not create or remove peptide. That is why two people holding identical vials can read completely different unit counts and both be correct.
Why does the calculator ask for an amount instead of telling me one?
Because it does not know what you are working with and it is not qualified to decide. This tool is arithmetic. It converts a number you supply into a concentration and a unit count, exactly as a calculator converts inches to centimetres without opinion about how long anything should be. Peptara Labs publishes education and the underlying research, not personal dosing advice, and any decision about use belongs with a qualified clinician.
What is a U-100 syringe and why are units used instead of mL?
A U-100 insulin syringe is calibrated in units, with 100 units to 1 mL. Reading 0.1 mL on a small barrel is easy to get wrong by a decimal place, and that misreading is the classic source of tenfold errors. Reading 10 unit ticks is unambiguous. The only mL figure that should appear in your own notes is the bacteriostatic water volume you added.
What if the calculator returns more than 100 units?
The arithmetic is still correct, it simply describes more than one 1 mL U-100 syringe can hold. A more concentrated solution, meaning less bacteriostatic water for the same vial, produces a smaller unit count. Two practical limits the arithmetic knows nothing about: the vial has to physically hold the volume you plan to add, and a count under about 5 units sits in the hardest part of the barrel to read.
What are the starting numbers in the calculator?
Placeholders, and nothing more. A 10 mg vial, 2 mL of bacteriostatic water and 1 mg to convert were chosen because they are round and divide cleanly, so the worked math is easy to follow at a glance. They are not a recommendation for any vial, any compound or any person. Replace all three with your own figures.
Can I use sterile water instead of bacteriostatic water?
They are different products, and the calculator does not care which one you used because the arithmetic is identical for any diluent volume. Bacteriostatic water for injection is sterile water containing 0.9 percent benzyl alcohol as a preservative, which is what allows a multi-use vial to be entered more than once. Sterile water for injection does not carry that preservative. The two vials look alike, so read the label rather than assuming.
General educational information only, research-use framing, not medical advice. This calculator performs arithmetic on numbers you supply and recommends nothing. Consult a qualified professional before acting.