mg to Units Converter
Convert an amount in mg or mcg into units on a U-100 syringe for the concentration on your vial, and back.
Arithmetic only · No sign-up · Runs in your browser
Draw to
25 units
01 Vial
Printed on the vial label, for example 2.5 mg/mL.
02 Dose
= 2500 mcg = 2.5 mg
03 Syringe (U-100)
Syringe size
- Volume
- 0.25 mL
- Concentration
- 10 mg/mL
| 5 units | 0.5 mg |
|---|---|
| 10 units | 1 mg |
| 20 units | 2 mg |
| 30 units | 3 mg |
| 50 units | 5 mg |
The starting values are examples. Replace them with what is on your vial label and prescription. This tool does the arithmetic only and does not recommend a dose.
mg to units
Units on an insulin syringe measure volume, not drug. On a U-100 syringe, 100 units fill 1 mL. The concentration on your vial links mg to mL, so every conversion needs it.
- mL = mg ÷ concentration in mg/mL
- Units = mL × 100
A vial labelled 10 mg/mL and an amount of 2.5 mg:
- Volume = 2.5 mg ÷ 10 mg/mL = 0.25 mL
- Units = 0.25 mL × 100 = 25 units
The same 2.5 mg from a 20 mg/mL vial is 0.125 mL, which is 12.5 units. The mg did not change, but the units did.
Units to mg
To go the other way, divide the units by 100 to get mL, then multiply by the concentration. At 10 mg/mL, 10 units is 0.1 mL × 10 mg/mL = 1 mg, which is 1,000 mcg.
Enter the mark you drew to and the concentration on your label:
The mark on a U-100 syringe.
Printed on the vial label, for example 10 mg/mL.
- Volume
- 0.1 mL
- Holds
- 1 mg
- Same in mcg
- 1000 mcg
How many units is 1, 2, 2.5 or 5 mg?
It depends on the concentration. The table works the formula through for four example concentrations. The amounts are examples to show the arithmetic, not doses. Use a column only if it matches the mg/mL printed on your vial.
| Amount | 2.5 mg/mL | 5 mg/mL | 10 mg/mL | 20 mg/mL |
|---|---|---|---|---|
| 1 mg | 40 units | 20 units | 10 units | 5 units |
| 2 mg | 80 units | 40 units | 20 units | 10 units |
| 2.5 mg | 100 units | 50 units | 25 units | 12.5 units * |
| 5 mg | Over 1 mL | 100 units | 50 units | 25 units |
Over 1 mL means the amount does not fit in a 100-unit syringe. * marks a draw that falls between the printed marks on 30, 50 and 100-unit syringes, so it cannot be drawn exactly. A 100-unit syringe is marked every 2 units, so odd numbers such as 25 fall between its marks too. The calculator above flags all of these.
mcg to units
1 mg is 1,000 mcg. Divide the mcg by 1,000 to get mg, then use the same formula. At 5 mg/mL, 250 mcg is 0.25 mg ÷ 5 mg/mL = 0.05 mL, which is 5 units. The calculator at the top takes mcg directly: switch the dose unit to mcg.
Example amounts at 5 mg/mL, to show the arithmetic:
| mcg | mg | mL | Units |
|---|---|---|---|
| 100 mcg | 0.1 mg | 0.02 mL | 2 units |
| 250 mcg | 0.25 mg | 0.05 mL | 5 units |
| 500 mcg | 0.5 mg | 0.1 mL | 10 units |
| 1,000 mcg | 1 mg | 0.2 mL | 20 units |
Syringe units and IU
A unit on a U-100 syringe is a volume: 0.01 mL of whatever is in the syringe. The IU printed on a vitamin or supplement label is a different kind of unit. It has nothing to do with syringe marks, and this page does not convert IU.
Before you draw
For a specific drug, the semaglutide dosage calculator and tirzepatide dosage calculator work through the same arithmetic for those vials. How to read an insulin syringe explains the marks.
This page does the arithmetic only and does not recommend a dose. Your dose comes from your prescriber. See the safety notes.
Common questions
How do I convert mg to units?
Divide the amount in mg by the concentration on your vial in mg/mL to get mL, then multiply by 100. At 10 mg/mL, 2.5 mg is 0.25 mL, which is 25 units on a U-100 syringe.
How many units is 2.5 mg?
It depends on the concentration on your vial. 2.5 mg is 100 units at 2.5 mg/mL, 50 units at 5 mg/mL, 25 units at 10 mg/mL and 12.5 units at 20 mg/mL. 12.5 units falls between the marks, so it cannot be drawn exactly.
How many mg is 10 units?
10 units is 0.1 mL. Multiply that by the concentration on your label: at 2.5 mg/mL it holds 0.25 mg, at 5 mg/mL 0.5 mg, at 10 mg/mL 1 mg and at 20 mg/mL 2 mg.
How do I convert mcg to units?
Divide the mcg by 1,000 to get mg, then divide by the concentration in mg/mL and multiply by 100. At 5 mg/mL, 250 mcg is 0.25 mg, which is 0.05 mL and 5 units.
Is a syringe unit the same as an IU?
Not the IU on a vitamin or supplement label. A syringe unit is a volume: 0.01 mL on a U-100 syringe. The IU on a label is a different kind of unit and has nothing to do with syringe marks. This page does not convert IU.