A peptide calculator turns three numbers, your vial size, the bacteriostatic water you add, and your target dose, into the exact number of units to draw on an insulin syringe. Enter those below and the tool runs the reconstitution and dosing math instantly, then helps you plan the cycle around it. I built it because I do this math every time I run a peptide, and getting it wrong wastes expensive product or doses you wrong.
Built and maintained by Nick Urban, School of Biohacking Instructor. Educational use only, not medical advice.
Key Takeaways
- Concentration (mg/mL) = peptide in the vial (mg) divided by bacteriostatic water added (mL).
- Draw volume (mL) = your dose (mg) divided by the concentration (mg/mL).
- On a U-100 insulin syringe, 100 units = 1 mL, so units to draw = draw volume (mL) times 100.
- Bacteriostatic water (BAC water) is the standard diluent; more water means a more dilute solution and an easier, larger draw.
- The same three inputs work for any injectable peptide: BPC-157, semaglutide, tirzepatide, TB-500, ipamorelin, and the rest.
How Do You Reconstitute a Peptide?
You reconstitute a peptide by adding bacteriostatic water to the dry powder, slowly, down the side of the vial, then swirling gently until it dissolves. Never shake it; shaking can damage the peptide. The amount of water you add sets the concentration, which is why the calculator asks for it: 5 mg of peptide in 2 mL of water gives 2.5 mg/mL, while the same 5 mg in 1 mL gives 5 mg/mL. Bacteriostatic water (water with 0.9 percent benzyl alcohol that suppresses bacterial growth) is the standard choice because a reconstituted vial is used over days or weeks.
How Much Bacteriostatic Water Should You Add?
Most people add 1 to 3 mL per vial, and the right amount is whatever makes your dose easy to measure. There is no single correct number; it is a tradeoff. Less water concentrates the peptide, so each dose is a tiny, hard-to-read draw. More water dilutes it, so the same dose becomes a larger, more accurate draw, at the cost of a bit more injected volume. The calculator lets you try a water amount and see the resulting units immediately, so you can pick a draw that lands on an easy-to-read mark on your syringe.
How Many Units Do You Draw on the Syringe?
On a U-100 insulin syringe, 100 units equals 1 mL, so each unit is 0.01 mL. To find your units, divide your dose by the concentration to get the draw in mL, then multiply by 100. Worked example: a 250 mcg (0.25 mg) dose from a 10 mg vial reconstituted with 1 mL of water sits at 10 mg/mL, so the draw is 0.025 mL, which is 2.5 units. The calculator does this in one step, but knowing the math lets you sanity-check any tool, including this one.
How Do You Calculate Peptide Concentration?
Concentration is peptide mass divided by liquid volume: milligrams in the vial divided by milliliters of water added, expressed as mg/mL. This single number drives every dose you draw afterward. It is the most common place people slip, usually by forgetting that a “5 mg” vial reconstituted with 2 mL is 2.5 mg/mL, not 5. Get the concentration right once per vial and every subsequent draw is simple division. The calculator stores it for you so you are not redoing the math each injection.
How Do You Plan a Peptide Cycle?
A cycle is the schedule: dose, frequency, how many weeks on, and how long off. The planner goes past the single-injection math to map the full cycle and the reconstitution you need to cover it, so you know how many vials a run will take. Where it goes further than a plain calculator is the evidence layer: each peptide links to its BioHarmony score, a 0 to 10 read on the strength of the human evidence, the safety profile, and the realistic benefit, so you are not just dosing accurately, you are dosing something worth dosing. You can also browse the full peptide protocol library for per-peptide ranges.
Which Peptides Can You Calculate Doses For?
Any injectable peptide, because the reconstitution math is identical regardless of the molecule. The tool covers the common ones, BPC-157, TB-500, ipamorelin, CJC-1295, tesamorelin, GHK-Cu, and the GLP-1 class (semaglutide, tirzepatide), plus the newer incretins. The dose ranges differ wildly between peptides, so the calculator pairs the math with sourcing guidance: if you are still choosing where to buy research material, start with the vetted list of top peptide companies and sources rather than the cheapest vial you can find.
Is Reconstituted Peptide Dosing Accurate?
It is accurate to the precision of your measurement, which is why the unit math matters. The biggest real-world errors are not the calculator; they are reading a tiny draw on a high-concentration vial, or assuming a vial’s labeled milligrams without confirming it. Two habits fix most of it: reconstitute to a concentration that puts your dose on an easy syringe mark, and treat any vial without a third-party certificate of analysis as an unknown quantity. The math is only as good as the inputs.
Frequently Asked Questions
What water do you use to reconstitute peptides? Bacteriostatic water for multi-dose vials used over days or weeks; sterile water only for a single same-day use, since it has no preservative.
Can I shake the vial to dissolve it faster? No. Add the water slowly down the side and swirl gently. Shaking can fragment the peptide.
How long does a reconstituted vial last? Refrigerated, commonly a few weeks; follow the specific peptide’s stability guidance and discard if the solution turns cloudy.
Does the calculator work for semaglutide and tirzepatide? Yes. The reconstitution and unit math is the same; only the dose ranges differ.
Educational information only. This is not medical advice, and nothing here is a recommendation to purchase or use any peptide. Talk to a qualified clinician.
