mg to Units Calculator

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.

mg to units reference (2.5 mg/mL, U-100)

Common concentration: a 5 mg vial reconstituted with 2 mL BAC water (2.5 mg/mL = 2,500 mcg/mL). Read off your own concentration in the calculator above.

Why you can’t convert mg to units without your concentration

Here’s the thing that trips everyone up: “units” on an insulin syringe don’t measure how much drug you’re taking. They measure volume, how far up the barrel the liquid goes. A U-100 syringe just means 100 units equals 1 mL. So 1 mg in a weak solution fills more units than 1 mg in a strong one, even though it’s the same dose. That’s why there’s no single “1 mg equals X units” answer. You have to pin your concentration first, then the units fall out of it.

How the conversion actually works

Two steps, and the calculator does both. First it works out the volume: your dose divided by your concentration. 1 mg at 2.5 mg/mL is 0.4 mL. Then it turns volume into units using your syringe: on a U-100, multiply mL by 100, so 0.4 mL is 40 units. On a U-40 the same 0.4 mL is 16 units. Same dose, same volume, different number on the barrel, because the syringe is scaled differently.

U-100 vs U-50 vs U-40: which syringe are you holding?

Most peptide and GLP-1 users are on U-100 (the standard 1 mL insulin syringe, 100 units to a mL). U-40 syringes are scaled for a more dilute liquid, so the same volume reads as fewer units. U-50 sits in between. The liquid you draw is identical, only the printed scale changes, so the one rule that matters: read the units off the syringe you’re actually holding, not someone else’s. If you’re not sure which you have, it’s printed on the barrel.

A quick worked example

Say you reconstituted a 5 mg vial with 2 mL of bacteriostatic water. That’s 2.5 mg/mL. You want a 2 mg dose. Volume is 2 ÷ 2.5, which is 0.8 mL. On your U-100 syringe that’s 80 units. Want 2.5 mg instead? That’s 1.0 mL, the full barrel, or 100 units. Set the concentration once and the whole table updates, so you’re not redoing the math every time you change your dose.

If you’d rather not re-derive this every cycle, log your concentration and each dose in Regimen and your draw amount is saved with every shot.

Download Regimen free - iOS·Android

Working in mcg or units instead? See the units to mL calculator, the units vs mL vs mg explainer, and how to read an insulin syringe.