Peptide Science Calculator
The math behind your dose — explained, visualized, and calculated in real time. Built for clarity, grounded in science.
Divide the total peptide in the vial by the volume of bacteriostatic water you added. This tells you how concentrated the solution is — how much peptide is dissolved in every milliliter.
Divide your target dose by the concentration. This gives you the exact volume of liquid that contains your desired amount of peptide.
A standard U-100 insulin syringe is calibrated so that 100 units = 1 ml. Multiply the volume in milliliters by 100 to get the unit mark you need to draw to.
Three equations turn a vial of powder into a precise dose.
Every peptide calculation comes down to three steps: figure out the concentration, work out the volume needed, then convert that volume to syringe units. Here’s exactly how each one works — and why.
Concentration
“How much peptide is in every milliliter of solution?”
Lyophilized (freeze-dried) peptides are weighed by mass. When you add water, the powder dissolves but adds negligible volume — so the final volume is essentially just the water you added. Dividing mass by volume gives concentration in mcg/ml.
More water = thinner solution = larger draws per dose. Less water = stronger solution = smaller, harder-to-measure draws. This is the lever you have over precision.
Dose Volume
“How much liquid contains my target dose?”
Once you know how concentrated the solution is, finding the dose volume is straightforward division. If your concentration is 2,500 mcg/ml and you want 250 mcg, you need one-tenth of a milliliter (250 ÷ 2,500 = 0.10).
The units must match. If concentration is in mcg/ml, the dose has to be in mcg. 1 mg = 1,000 mcg — converting upstream prevents the most common dosing errors.
Syringe Units
“What number on the syringe do I draw to?”
A standard U-100 insulin syringe is calibrated so 100 units = 1 ml. Each unit on the scale equals 0.01 ml. Measuring in units rather than milliliters lets you be ten times more precise — critical for peptide microdoses.
For a U-40 syringe (less common), you’d multiply by 40 instead, since 40 units = 1 ml.
Why the chemistry works
Why bacteriostatic water?
BAC water is sterile water with 0.9% benzyl alcohol. The alcohol is bacteriostatic — it prevents bacterial growth without sterilizing — which lets you re-enter the same vial multiple times across roughly 28 days. Plain saline or sterile water without preservative would risk contamination after the first puncture.
Why lyophilized powder?
Most therapeutic peptides are unstable in solution — they break down within hours or days. Lyophilization (freeze-drying) removes the water, leaving a stable powder that ships and stores for months. Reconstitution with BAC water revives it on demand.
Why 100 units = 1 ml?
The U-100 standard was created for insulin (originally 100 IU per ml). Each tiny mark on the syringe represents 0.01 ml — fine enough to measure peptide doses as small as 50 mcg accurately. The U-100 ratio is now the universal calibration for insulin syringes worldwide.
Why mass/volume, not mass/mass?
Concentration is expressed as mass per volume (mcg/ml) because syringes draw by volume. Drawing 0.10 ml of a 2,500 mcg/ml solution always delivers 250 mcg — regardless of room temperature or solution density — because volume measurement is reliable in liquid form.
Full worked example
5 mg vial of BPC-157 · 2 ml BAC water · 250 mcg target dose
Draw to the 10-unit mark on a U-100 insulin syringe. ✓
Quick conversion reference
The constants you’ll use repeatedly when reading vial labels and choosing syringes.