mg to units calculator: how to convert on a syringe
Divide the dose in mg by the strength in mg/mL, then multiply by 100. That works because a U-100 insulin syringe is marked so that 100 units fill 1 mL, so each unit line is 0.01 mL.[1]
1. volume (mL) = dose (mg) ÷ strength (mg/mL)
2. units = volume (mL) × 100
Example. A liquid labelled 5 mg/mL and a dose of 1.5 mg: 1.5 ÷ 5 = 0.3 mL. 0.3 × 100 = 30 units, which fills a 0.3 mL syringe to its top line.
mg to units syringe chart
Find your dose on the left and your strength across the top. Dashes mean over 100 units: more than the largest common insulin syringe, 1 mL, holds.[2]
| Dose | 1 mg/mL | 2 mg/mL | 5 mg/mL | 10 mg/mL | 20 mg/mL |
|---|---|---|---|---|---|
| 0.1 mg | 10 | 5 | 2 | 1 | 0.5 |
| 0.25 mg | 25 | 12.5 | 5 | 2.5 | 1.25 |
| 0.5 mg | 50 | 25 | 10 | 5 | 2.5 |
| 1 mg | 100 | 50 | 20 | 10 | 5 |
| 1.5 mg | – | 75 | 30 | 15 | 7.5 |
| 2 mg | – | 100 | 40 | 20 | 10 |
| 2.5 mg | – | – | 50 | 25 | 12.5 |
| 5 mg | – | – | 100 | 50 | 25 |
| 10 mg | – | – | – | 100 | 50 |
1.5 mg to units and 2 mg to units on an insulin syringe
1.5 mg is 15 units at 10 mg/mL and 30 units at 5 mg/mL; 2 mg is 20 units at 10 mg/mL and 40 units at 5 mg/mL. On a U-100 insulin syringe, insulin units and volume lines are the same thing only for U-100 insulin; for any other liquid the lines are 0.01 mL volume marks, so the strength decides the answer. 1 mL syringes come with 1-unit or 2-unit lines, so check yours before reading an odd number such as 15.[3]
Where to find the strength
The strength is printed on the label, usually as mg/mL (for example “10 mg/mL”) or as a total amount in a total volume (“20 mg/2 mL”, which is also 10 mg/mL). If a medicine is mixed from a powder, use the final strength given on the label or by your pharmacist. Enter either form in the calculator: amount in the first box, volume in the second. A label total can also be turned into mg/mL with the strength calculator.
Your prescriber or pharmacist tells you the dose; this calculator only converts it. After drawing up, look at the syringe again to make sure it holds the right dose.[1]
Charts for single doses
- 0.25 mg to unitsSmall-dose chart and why errors grow
- 0.5 mg to unitsHalf a milligram at every strength
- 1 mg to unitsThe 100 ÷ strength shortcut
- 2.5 mg to unitsHalf-unit results and the 1 mL limit
- 5, 7.5 and 10 mg to unitsWhen a dose fits an insulin syringe
- mcg to unitsDoses written in micrograms
Common mg to units mistakes
The most common mg to units mistakes are reading units as milligrams and using the wrong strength. Check these before you draw up:
- Units are not mg. 20 units is 0.2 mL; it is 2 mg only at 10 mg/mL. Work it out with units to mg.
- Using the label total as the strength. “20 mg/2 mL” is 10 mg/mL, not 20. The concentration calculator converts it.
- mcg entered as mg. 250 mcg is 0.25 mg; a slip is a 1,000-fold error. Use mcg to units for microgram doses.
- Assuming 1 line = 1 unit. Some 1 mL syringes are marked every 2 units.[3] See how to read an insulin syringe.
- Treating syringe units as IU. A syringe unit is a volume mark; an international unit is a measure of activity. ISMP advises writing “units”, not “IU”.[4]
How we checked these numbers
Every result on this page comes from the same code as the calculator, and the known answers below are run as tests before each release.
| Input | Expected | Basis |
|---|---|---|
| 2.5 mg at 10 mg/mL | 25 units (0.25 mL) | units = mg ÷ (mg/mL) × 100 |
| 1.5 mg at 5 mg/mL | 30 units | same |
| 2.5 mg at 3 mg/mL | 83.33 units, flagged between lines | same; 1 mL syringe line check |
| 5 mg at 2 mg/mL | 2.5 mL, flagged over 1 mL | capacity check |
Known limits.
- Assumes a U-100 syringe. U-40 and U-500 scales need their own conversion.
- Line-spacing warnings assume 1-unit lines on 0.3 and 0.5 mL syringes and 2-unit lines on 1 mL; check your syringe.
Download the data. mg to units chart, 0.1–10 mg × 1–100 mg/mL (CSV)
Change log.
- : Calculator, chart, shareable links and between-line warnings published.
Frequently asked questions
How do you convert mg to units?
Divide the dose in mg by the strength in mg/mL to get mL, then multiply by 100 to get units on a U-100 syringe. Units = mg ÷ (mg/mL) × 100.
How many units is 1 mg?
At 10 mg/mL, 1 mg is 10 units. At 5 mg/mL it is 20 units. At 1 mg/mL it is 100 units. There is no single answer without the strength. See 1 mg to units syringe chart.
How many units is 2 mg on an insulin syringe?
At 10 mg/mL it is 20 units (0.2 mL); at 5 mg/mL it is 40 units (0.4 mL).
Are insulin units the same as these units?
For U-100 insulin, yes: one unit of insulin is one 0.01 mL line. For any other liquid, the lines are just volume marks and the amount of drug in each depends on its strength.
Are syringe units the same as IU?
Not in general. A syringe unit is a 0.01 mL line on a U-100 syringe; an international unit measures a drug’s activity. They match only for U-100 insulin in a U-100 syringe. ISMP lists “IU” as error-prone and advises writing “units”.
What if the answer is not on a syringe line?
If the result falls between lines, such as 12.5 units on a syringe with 1-unit lines, ask your pharmacist how to measure it. Do not round on your own.
What if my label gives mg and mL separately?
Divide the mg by the mL to get the strength: 20 mg in 2 mL is 10 mg/mL. Or enter the two numbers in the strength boxes as they are printed.
Can I use this for U-40 or U-500 syringes?
No. This page assumes U-100 syringes. For other scales see mL to units and the U-40 conversion chart.