units = amount mg ÷ mg/mL × 100
The × 100 is the syringe scale: "U-100" means 100 units per mL, the point most often misread in reported syringe errors (Grissinger, P&T 2015).
mg to units chart by concentration
U-100 units for each amount (rows) at each concentration (columns). Amber values are larger than a 1 mL barrel holds.
| Amount | 1 mg/mL | 2 mg/mL | 2.5 mg/mL | 5 mg/mL | 10 mg/mL | 15 mg/mL | 20 mg/mL |
|---|---|---|---|---|---|---|---|
| 0.1 mg | 10 | 5 | 4 | 2 | 1 | 0.7 | 0.5 |
| 0.25 mg | 25 | 12.5 | 10 | 5 | 2.5 | 1.7 | 1.3 |
| 0.5 mg | 50 | 25 | 20 | 10 | 5 | 3.3 | 2.5 |
| 1 mg | 100 | 50 | 40 | 20 | 10 | 6.7 | 5 |
| 1.5 mg | 150 | 75 | 60 | 30 | 15 | 10 | 7.5 |
| 2 mg | 200 | 100 | 80 | 40 | 20 | 13.3 | 10 |
| 2.5 mg | 250 | 125 | 100 | 50 | 25 | 16.7 | 12.5 |
| 3 mg | 300 | 150 | 120 | 60 | 30 | 20 | 15 |
| 4 mg | 400 | 200 | 160 | 80 | 40 | 26.7 | 20 |
| 5 mg | 500 | 250 | 200 | 100 | 50 | 33.3 | 25 |
How do you convert mcg to units?
Micrograms work the same way once they are in milligrams: 1,000 mcg = 1 mg, so divide by 1,000 first. units = (mcg ÷ 1,000) ÷ mg/mL × 100. Small peptides are often written in mcg while vials are labeled in mg, which is where a factor-of-1,000 slip can creep in. Single-amount pages: 200 mcg, 250 mcg, 500 mcg.
| Amount | 1 mg/mL | 2 mg/mL | 2.5 mg/mL | 5 mg/mL |
|---|---|---|---|---|
| 50 mcg | 5 | 2.5 | 2 | 1 |
| 100 mcg | 10 | 5 | 4 | 2 |
| 200 mcg | 20 | 10 | 8 | 4 |
| 250 mcg | 25 | 12.5 | 10 | 5 |
| 300 mcg | 30 | 15 | 12 | 6 |
| 500 mcg | 50 | 25 | 20 | 10 |
| 750 mcg | 75 | 37.5 | 30 | 15 |
| 1,000 mcg | 100 | 50 | 40 | 20 |
Why mg to units always needs a concentration
Milligrams measure how much substance there is; syringe units measure volume. The bridge between the two is the concentration, which you create when you add water to a vial. Double the water and each unit holds half as much, so the same milligrams take twice as many units. That's why a units figure copied from somewhere else is only valid if your vial size and water volume are identical. When in doubt, recompute with the peptide calculator.
FDA has warned about exactly this confusion with compounded multi-dose vials, where instructions written in "units" were misread.
Frequently asked questions
How do I convert mg to units?
Divide the mg by the concentration in mg/mL to get milliliters, then multiply by 100 for a U-100 syringe. 1 mg at 5 mg/mL = 0.2 mL = 20 units.
How many units is 1 mg?
There is no fixed answer: it depends on the concentration. At 10 mg/mL 1 mg is 10 units; at 5 mg/mL it is 20 units; at 2.5 mg/mL it is 40 units; at 1 mg/mL it is 100 units.
How many units is 2.5 mg?
At 5 mg/mL (10 mg in 2 mL), 2.5 mg = 0.5 mL = 50 units on U-100. At 10 mg/mL it is 25 units.
How do I convert mcg to units?
Divide the mcg by 1,000 to get mg, then use the same formula. 250 mcg is 0.25 mg; at 5 mg/mL that is 0.05 mL, or 5 units on a U-100 syringe. At 2.5 mg/mL it is 10 units.
How do I find the concentration?
Divide the total mg in the vial by the mL of water you added. A 10 mg vial with 2 mL is 5 mg/mL.
Sources
- FDA alerts health care providers, compounders and patients of dosing errors associated with compounded injectable semaglutide products
- A Clinical Reminder About the Safe Use of Insulin Vials (Grissinger M.)
- Analysis of factors affecting the accuracy of low-dose insulin dosage using syringes and vials (Kondo M. et al.)
Links checked 2026-10-19.