Peptide dose calculator
To convert a peptide dose to syringe units, divide vial strength in mg by the water added in mL for concentration, divide your dose by that, then multiply by 100 for a U-100 syringe. At 2.5 mg/mL, a 250 mcg dose is 10 units.
One dose, three numbers
A dose calculation only ever needs vial strength, the water you added and the dose you want. The calculator above does the arithmetic, but it is worth knowing the shape of it so a wrong answer is obvious.
Concentration is strength divided by volume. Volume to draw is dose divided by concentration. Units are that volume multiplied by 100 on a U-100 syringe, or by 40 on a U-40 syringe.
- Write down the vial strength in mg exactly as printed.
- Write down the bacteriostatic water you added, in mL.
- Convert your dose to mg if the concentration is in mg/mL — 250 mcg is 0.25 mg.
- Divide the dose by the concentration to get mL.
- Multiply by 100 for U-100 units, or by 40 for U-40 units.
Single-dose conversions at common concentrations
Read across the concentration you actually mixed. Anything landing at one or two units is too concentrated to measure safely — use more diluent next vial.
| Concentration | 100 mcg | 250 mcg | 500 mcg | 1 mg |
|---|---|---|---|---|
| 1 mg/mL | 10 units | 25 units | 50 units | 100 units |
| 2 mg/mL | 5 units | 12.5 units | 25 units | 50 units |
| 2.5 mg/mL | 4 units | 10 units | 20 units | 40 units |
| 5 mg/mL | 2 units | 5 units | 10 units | 20 units |
| 10 mg/mL | 1 unit | 2.5 units | 5 units | 10 units |
Dose errors worth double-checking
- mcg entered where the field expects mg, or the reverse — a 1,000-fold difference.
- Calculating for U-100 and drawing on a U-40 or U-50 barrel.
- Using the vendor's suggested water volume rather than the volume you actually added.
- Rounding a 12.5-unit draw to 12 or 13 on a syringe with only whole-unit markings.
- Assuming a blend vial's total mg is the dose of each component. Blends need per-component math.
- Treating an unverified vendor strength as exact. Without a batch certificate of analysis, it is an estimate.
Free dose calculator
Convert your dose to syringe units
Enter your vial, water volume and dose. You get the exact units to draw, plus a chart of nearby doses at the same concentration.
Your conversion chart
Syringe marks converted using your concentration. These are reference values, not suggested doses.
| Syringe | Volume | Amount |
|---|---|---|
| 10 units · yours | 0.1 mL | 250 mcg |
| 20 units | 0.2 mL | 500 mcg |
| 30 units | 0.3 mL | 750 mcg |
| 40 units | 0.4 mL | 1,000 mcg |
| 50 units | 0.5 mL | 1,250 mcg |
| 60 units | 0.6 mL | 1,500 mcg |
| 70 units | 0.7 mL | 1,750 mcg |
| 80 units | 0.8 mL | 2,000 mcg |
| 90 units | 0.9 mL | 2,250 mcg |
| 100 units | 1 mL | 2,500 mcg |
Frequently asked questions
- How many units is one peptide dose?
- Units depend on concentration, not on the dose alone. Divide vial strength in mg by diluent volume in mL, divide your dose by that concentration, then multiply by 100. A 5 mg vial in 2 mL is 2.5 mg/mL, so 250 mcg is 0.1 mL, which is 10 units on a U-100 syringe.
- How do I convert mcg to mg for a dose?
- Divide micrograms by 1,000 to get milligrams: 250 mcg is 0.25 mg, 500 mcg is 0.5 mg, 1,500 mcg is 1.5 mg. Mixing the two units inside one calculation is the most common way people end up with a tenfold dosing error.
- Is a unit the same as a milligram?
- No. A unit is a volume marking on an insulin syringe — on U-100, one unit is 0.01 mL. How much peptide sits in that volume depends entirely on how concentrated your vial is, so the same 10 units can be two very different doses.
- What changes on a U-40 syringe?
- A U-40 barrel puts 40 units in 1 mL, so each unit is 0.025 mL — two and a half times the volume of a U-100 unit. Using U-100 numbers on a U-40 syringe delivers roughly 2.5 times the intended dose. Check the barrel before drawing.
- Can I measure a dose smaller than one unit?
- Not reliably. If your dose lands under about five units, add more bacteriostatic water so the same dose occupies a larger, readable volume. Most people can read a 10–30 unit draw accurately; below that, small errors become large percentages.
- Does the dose change if I add more water?
- The dose in micrograms does not change, but the volume you draw does. More water means a lower concentration, so the same dose becomes more units. That is why the water volume has to be written on the vial and used consistently.
References & evidence
Sources cited on this page. Last reviewed September 2026. Corrections: editorial policy.
- US Food and Drug Administration. Information regarding insulin storage and syringe dose accuracy. https://www.fda.gov/drugs/emergency-preparedness-drugs/information-regarding-insulin-storage-and-switching-between-products-emergency
- Institute for Safe Medication Practices. ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations. https://www.ismp.org/recommendations/error-prone-abbreviations-list
- US Pharmacopeia. General Chapter <797> Pharmaceutical Compounding — Sterile Preparations. https://www.usp.org/compounding/general-chapter-797
Stop converting by hand every time
Save the vial once and DoseRoutine shows the exact units for each scheduled dose, flags draws too small to measure accurately, and keeps a log of what you actually injected.
Start free in DoseRoutineEducational reference only, not medical advice. Talk to a qualified clinician before starting, stopping or combining any peptide, supplement or medication.