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U-100 · U-50 · U-40 insulin syringe

Units to mg Calculator

You know how many units you drew. This tells you how many milligrams that is, once you add your concentration. It also shows the volume in mL.

Updated September 2026

Use mcg/mL for most peptides, mg/mL for compounded GLP-1.

Draw syringe to

0 units

(0.00 mL)

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Your dose
100 units = 1mL

Units measure volume on the syringe, not the amount of drug. The same dose is a different number of units at a different concentration, so always set your concentration first.

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units → mg on U-100

UnitsVolume (mL)Dose (mg)
5 units0.05125 mcg
10 units0.10250 mcg
20 units0.20500 mcg
25 units0.25625 mcg
50 units0.501.25 mg
75 units0.751.875 mg
100 units1.002.5 mg

This calculator is for informational purposes only, so always double-check your result with a healthcare provider. We assume no liability for dosing decisions made from it.

How to use it

How to use this calculator

  1. 01

    Enter your concentration

    The mg per mL after mixing. If you only know your vial size and how much water you added, open the helper and it works it out.

  2. 02

    Pick your syringe

    U-100 is the standard 1 mL insulin syringe. U-50 and U-40 use a different scale, and the same units mean a different volume.

  3. 03

    Type the units

    The units marked on the barrel. The calculator returns the dose in mg (or mcg) and the volume in mL.

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Questions

units to mg questions

How many mg is 50 units?
It depends on your concentration, because units measure volume, not drug. On a U-100 syringe, 50 units is 0.5 mL. At 2.5 mg/mL that is 1.25 mg; at 5 mg/mL it is 2.5 mg; at 10 mg/mL it is 5 mg. Enter your own concentration above to get the exact number.

How many mg is 10 units on an insulin syringe?
10 units on a U-100 syringe is 0.1 mL. At 2.5 mg/mL that is 0.25 mg; at 5 mg/mL it is 0.5 mg. If your vial is labelled in mcg/mL, switch the concentration unit and the answer comes back in mcg.

How do you convert units to mg?
Two steps. First, units to mL: divide by 100 on a U-100 syringe (50 on a U-50, 40 on a U-40). Then mL to mg: multiply by your concentration in mg/mL. 20 units on a U-100 is 0.2 mL, and at 5 mg/mL that is 1 mg.

Is 1 mg equal to 1 unit?
No. A unit is a volume mark on the syringe (0.01 mL on a U-100). A milligram is an amount of drug. How many units make 1 mg depends entirely on how concentrated the liquid is, which is why this calculator asks for your concentration first.

How many mg is 100 units?
100 units is the full 1 mL barrel on a U-100 syringe. At 2.5 mg/mL that is 2.5 mg; at 5 mg/mL it is 5 mg. On a U-40 syringe, 100 units would be 2.5 mL, more than the syringe holds, so check your syringe type.

How many mg is 25 units?
On a U-100 syringe, 25 units is 0.25 mL. At 2.5 mg/mL that is 0.625 mg (the calculator shows it as 625 mcg); at 5 mg/mL it is 1.25 mg. This is a common draw for a 0.25 mg semaglutide start at 1 mg/mL, and for 1.25 mg of tirzepatide at 5 mg/mL.

I don't know my concentration. What do I do?
Open the helper under the concentration box and enter your vial size in mg and the bacteriostatic water you added in mL. Concentration is just vial size divided by water: a 5 mg vial in 2 mL of water is 2.5 mg/mL.

Does the syringe type change the mg?
Yes. The same number of units is a different volume on a U-40, U-50, and U-100 syringe, so it is a different amount of drug. 40 units is 0.4 mL on a U-100 but a full 1 mL on a U-40. Always pick the syringe you are actually holding.

What is the dose in mcg instead of mg?
Anything under 1 mg shows in mcg automatically. 10 units at 1 mg/mL on a U-100 is 0.1 mL, which the calculator shows as 100 mcg. Most peptides are dosed in mcg, most compounded GLP-1s in mg.

Why does the dose change when I change concentration?
Because the units did not change but the amount of drug in each mL did. 50 units is always 0.5 mL on a U-100; whether that 0.5 mL holds 1.25 mg or 2.5 mg depends on how you mixed the vial. This is the single most common source of dosing mistakes.

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