Published by Peptide Protocols · Reviewed September 2026 · How we make these pages · Educational & research purposes only — not medical advice.
1 mL = 100 units on a U-100 insulin syringe. Formula: mg ÷ mL = mg/mL; (mcg ÷ 1000) ÷ mg/mL = mL; mL × 100 = units.
Units to draw on a U-100 insulin syringe for the common vial sizes and water volumes. Pick the row that matches your vial and the water you added.
| Vial + water | Concentration | 500 mcg | 1 mg | 1.5 mg |
|---|---|---|---|---|
| 10 mg vial + 1 mL water | 10 mg/mL | 5 u | 10 u | 15 u |
| 10 mg vial + 2 mL water | 5 mg/mL | 10 u | 20 u | 30 u |
| 10 mg vial + 3 mL water | 3.33333 mg/mL | 15 u | 30 u | 45 u |
| 5 mg vial + 1 mL water | 5 mg/mL | 10 u | 20 u | 30 u |
| 5 mg vial + 2 mL water | 2.5 mg/mL | 20 u | 40 u | 60 u |
| 5 mg vial + 3 mL water | 1.66667 mg/mL | 30 u | 60 u | 90 u |
Worked example: a 10 mg vial with 2 mL of bacteriostatic water is 5 mg/mL. A 1 mg draw is 0.20 mL, which is 20 units. Change the water and every number on the syringe changes — which is the single most common reconstitution mistake. The full explanation is in How to Reconstitute Peptides.
With 2 mL of water in a 10 mg vial (5 mg/mL), 1 mg = 0.2 mL = 20 units. With 1 mL (10 mg/mL) it is 10 units; with 3 mL (3.33 mg/mL) it is 30 units.
2 mL is the most common: it puts 500 mcg on 10 units and 1 mg on 20 units, easy lines to read. The chart below covers 1, 2 and 3 mL.
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The one formula, a BAC-water chart, and the 10 most-researched beginner peptides — the math done for you. Print it for the fridge.
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