Syringes
Syringe Units Explained: U-100 vs U-50 vs U-40
Insulin syringes are marked in "units," not milliliters, and the number you read depends on which syringe you have. Here's what U-100, U-50, and U-40 mean and how to convert a volume in mL to units.
What a "unit" means
The U-number is the syringe's scale: units per milliliter. A U-100 syringe is marked so that 1 mL = 100 units. So one unit on a U-100 syringe is 0.01 mL of liquid. The unit mark is just an easier way to read very small volumes.
How the three scales compare
| Syringe | Units per mL | 1 unit equals | 0.10 mL reads as |
|---|---|---|---|
| U-100 | 100 | 0.01 mL | 10 units |
| U-50 | 50 | 0.02 mL | 5 units |
| U-40 | 40 | 0.025 mL | 4 units |
Notice that the same volume of liquid (0.10 mL) reads as a different number of units on each syringe. That's why you must always match your calculator's syringe setting to the syringe in your hand.
Converting mL to units
U-100: mL × 100 · U-50: mL × 50 · U-40: mL × 40
Example: you calculated a dose of 0.2 mL. On a U-100 syringe that's 20 units; on a U-50 it's 10 units; on a U-40 it's 8 units. Same liquid, different mark.
Let the calculator pick the units
Choose U-100, U-50, or U-40 and the calculator converts your dose to the right unit mark automatically.
Open the free calculatorWhich syringe should the calculator use?
Use whichever syringe you physically have. U-100 insulin syringes are the most common. If your syringe is labeled U-40 or you're using a half-unit (U-50-style) syringe, set the calculator to match; otherwise the unit number it gives won't line up with the marks you're reading.
This guide is for calculation and educational purposes only and is not medical advice. It does not recommend any peptide, dose, or protocol. Always consult a qualified clinician before starting, changing, or stopping any peptide.