mg to Units Calculator
Milligrams cannot be converted to syringe units without knowing the concentration, because units measure volume rather than mass. Divide the dose in milligrams by the concentration in mg/mL to get millilitres, then multiply by 100 for a U-100 syringe.
The formula
units = (mg ÷ mg per mL) × 100
On a U-100 insulin syringe, 100 units is 1 mL and 1 unit is 0.01 mL. The conversion from milligrams therefore always passes through volume, which is why the concentration is required.
Convert a dose to syringe units
Enter the concentration from your label, or use vial strength and water volume to calculate it.
Example values are prefilled. Replace them with your own.
- Concentration
- 2.5 mg/mL
- Volume to draw
- 0.1 mL
- Per unit
- 25 mcg
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Worked examples
Milligram-to-unit conversions at four common concentrations.
2.5 mg/mL concentration
10units
- Concentration
- 2.5 mg/mL
- Dose
- 0.25 mg
- Volume
- 0.1 mL
5 mg/mL concentration
10units
- Concentration
- 5 mg/mL
- Dose
- 0.5 mg
- Volume
- 0.1 mL
10 mg/mL concentration
10units
- Concentration
- 10 mg/mL
- Dose
- 1 mg
- Volume
- 0.1 mL
1 mg/mL concentration
50units
- Concentration
- 1 mg/mL
- Dose
- 0.5 mg
- Volume
- 0.5 mL
Frequently asked questions
- Can I enter the mg/mL from my label directly?
- Yes. Choose ‘I know the mg/mL’, enter the concentration in mg per mL, then enter the dose in mg and select your syringe scale. You do not need to enter a vial strength or water volume. If you need to calculate concentration instead, choose ‘Use vial + water’.
- How many units is 1 mg?
- There is no single answer without a concentration. At 1 mg/mL, 1 mg is 100 units. At 5 mg/mL it is 20 units, and at 10 mg/mL it is 10 units.
- Are units the same as milligrams?
- No. Units are a volume marking on the syringe barrel — 100 units equals 1 mL on a U-100 syringe. The mass in milligrams that a unit represents depends entirely on your concentration.
- How do I convert units back to mg?
- Divide the units by 100 to get millilitres, then multiply by the concentration in mg/mL. For example, 20 units at 5 mg/mL is 0.2 mL, which is 1 mg.
- What is mcg per unit?
- Multiply the concentration in mg/mL by 1000 to get mcg/mL, then divide by 100 for a U-100 syringe. At 2.5 mg/mL, each unit contains 25 mcg.