Solution math
Peptide reconstitution calculator
How to reconstitute a research peptide, with the syringe math done for you. Fill in any three of mg per vial, bacteriostatic water, target per draw, and draw volume — the calculator solves the one you leave blank. Pick your syringe (insulin U-100 or a standard 1–10 mL) and the draw amount and diagram switch to match.
What this calculator does
Research peptides usually arrive as a dry powder that has to be mixed with liquid before any amount can be measured out. This calculator handles the two numbers that matter once you add the liquid: how strong the mixture is, and exactly what mark to draw to on your syringe for the amount your protocol calls for — whether that's an insulin syringe marked in units or a standard syringe marked in millilitres.
How to use it
- mg per vialEnter the milligrams (mg) of peptide printed on the vial label — for example, 5 mg. Tap a preset or type any amount; the field accepts whatever you enter.
- Bacteriostatic waterEnter how many millilitres (mL) of bacteriostatic water you're adding. ("Bacteriostatic" just means it has a tiny amount of preservative that stops bacteria growing.) More water makes a weaker, more dilute mixture — and a bigger number to draw for the same amount. A standard small peptide vial holds about 3 mL of liquid at most, so 1–3 mL is the usual range.
- Target amount per drawEnter the amount one draw should contain, in micrograms (mcg) or milligrams (mg) using the toggle. This is a number you decide from your protocol — the tool never picks it for you. Typical amounts for each compound are in the dosing guides.
- SyringePick the syringe you'll measure with. Insulin syringes are marked in "units" (U-100: 100 units = 1 mL) and come in 0.3, 0.5, and 1 mL barrels; standard syringes (1–10 mL) are marked in millilitres. The result and the diagram below switch to match — so if you have a 3 mL syringe, the answer reads in mL.
- Draw volumeThe mark to draw up to, shown in your chosen syringe's scale (units for insulin, mL for standard). Leave this — or any one of the three fields above — blank, and the calculator fills it in.
Reading your results
- Draw to ___The mark to fill the syringe to, in the unit your selected syringe uses. The diagram redraws to that syringe and shows where the draw lands; if a draw won't fit, it warns you to pick a larger one.
- ConcentrationHow strong the mixture is — milligrams of peptide in each millilitre of liquid (mg/mL).
- Doses per vialRoughly how many draws of your target amount the whole vial holds.
A worked example
A 5 mg vial, mixed with 2 mL of bacteriostatic water, for a 250 mcg target, on a 1 mL insulin syringe:
5 mg ÷ 2 mL = 2.5 mg/mL (concentration)
250 mcg = 0.25 mg; 0.25 ÷ 2.5 = 0.1 mL
0.1 mL × 100 = draw to 10 units — or simply 0.1 mL on a standard syringe
5 mg ÷ 0.25 mg = 20 draws in the vial
Common questions
Can I use a 3 mL (non-insulin) syringe?
Yes — choose "Standard · 3 mL" from the Syringe menu. The result switches to millilitres and the diagram is marked in mL, so you read the draw straight off a standard syringe.
How much water can the vial hold?
The standard small peptide vial (sold as "2 mL" or "3 mL") holds about 3 mL of liquid at most, so 1–3 mL of bacteriostatic water is the practical range. Amounts above 3 mL will not fit the vial.
What is bacteriostatic water?
Sterile water with a small amount of benzyl alcohol that limits bacterial growth. It's the liquid commonly used to reconstitute — that is, dissolve — lyophilized (freeze-dried) peptide powder.
What's a U-100 syringe?
An insulin syringe whose barrel is marked 0–100 "units," where 100 units equals 1 mL. Reading the answer in units saves you measuring out tiny millilitre fractions by eye.
Does it matter how much water I add?
It changes the concentration, not the amount of peptide. More water means a weaker mixture and a larger number on the syringe for the same target. Pick a water amount that lands your draw on an easy-to-read mark.
How do I reconstitute a 10 mg peptide vial?
Enter 10 in mg per vial, the amount of bacteriostatic water you are adding (2 mL is a common choice, giving 5 mg/mL), and your target per draw. With 2 mL of water, a 250 mcg target draws to 5 units on a U-100 syringe and a 1 mg target draws to 20 units. The 10 mg size is the most common research vial — BPC-157, TB-500, semaglutide, tirzepatide, retatrutide, tesamorelin and MOTS-c are all sold at 10 mg.
How many units is 250 mcg?
It depends on the concentration, which is why the calculator asks for the vial and water first. At 2.5 mg/mL (a 5 mg vial in 2 mL) 250 mcg is 10 units; at 5 mg/mL (a 10 mg vial in 2 mL) it is 5 units. Units are a volume, not an amount of peptide.
Why does it say "research use only"?
These tools do measurement arithmetic for laboratory research. They don't recommend amounts and aren't medical guidance.
The math, for the curious
The four quantities are linked by one relationship: draw (mL) = target (mg) × water (mL) ÷ vial (mg).
Give any three and the fourth follows. Concentration is vial (mg) ÷ water (mL); on a U-100 insulin syringe, 1 mL = 100 units; standard syringes read directly in mL; and doses per vial is vial ÷ target, rounded down.