Syringe scales
A unit is a mark on a barrel, not a volume. These are the calibrations behind the marks.
Educational arithmetic only. Not medical advice and not a dosing protocol.
| Barrel | Units per mL | Capacity | Capacity in units | Graduation | Volume of one unit |
|---|---|---|---|---|---|
| U-100, 1 mL | 100 | 1 mL | 100 units | every 1 unit | 0.0100 mL |
| U-100, 0.5 mL | 100 | 0.5 mL | 50 units | every 1 unit | 0.0100 mL |
| U-100, 0.3 mL | 100 | 0.3 mL | 30 units | every 1 unit | 0.0100 mL |
| U-50, 0.5 mL | 50 | 0.5 mL | 25 units | every 1 unit | 0.0200 mL |
| U-40, 1 mL | 40 | 1 mL | 40 units | every 1 unit | 0.0250 mL |
The same volume on every barrel
| Volume | U-100, 1 mL | U-100, 0.5 mL | U-100, 0.3 mL | U-50, 0.5 mL | U-40, 1 mL |
|---|---|---|---|---|---|
| 0.02 mL | 2.00 | 2.00 | 2.00 | 1.00 | 0.80 |
| 0.05 mL | 5.00 | 5.00 | 5.00 | 2.50 | 2.00 |
| 0.1 mL | 10.00 | 10.00 | 10.00 | 5.00 | 4.00 |
| 0.15 mL | 15.00 | 15.00 | 15.00 | 7.50 | 6.00 |
| 0.2 mL | 20.00 | 20.00 | 20.00 | 10.00 | 8.00 |
| 0.25 mL | 25.00 | 25.00 | 25.00 | 12.50 | 10.00 |
| 0.3 mL | 30.00 | 30.00 | 30.00 | 15.00 | 12.00 |
| 0.5 mL | 50.00 | 50.00 | 50.00 † | 25.00 | 20.00 |
| 0.75 mL | 75.00 | 75.00 † | 75.00 † | 37.50 † | 30.00 |
| 1 mL | 100.00 | 100.00 † | 100.00 † | 50.00 † | 40.00 |
Read this with the answer
This is educational arithmetic on figures entered by the reader. It is not medical advice, not a dosing protocol, and not a recommendation that anything be prepared, obtained or administered.
Nothing here states what quantity is appropriate for anyone, and there is no function in it that produces an amount to administer. A question about anyone’s health belongs with a licensed clinician who can examine the person asking.
Most compounds named here are research chemicals that are not approved by the FDA for human use. An exact calculation is not an accurate measurement: what is actually in a syringe depends on the preparation and the device, neither of which this page can see.
No qualified clinical reviewer is recorded against this site, and no credential is claimed anywhere on it. Full disclaimer.
What the U number means
The number after the U is how many units the barrel prints per millilitre. A U-100 barrel is marked so that 100 of its units fill 1 mL, which makes one unit 0.01 mL. A U-40 barrel prints 40 units per millilitre, so one of its units is 0.025 mL: two and a half times as much liquid behind the same printed number.
The convention exists because these barrels were designed for insulin preparations standardised at those strengths, and the units on them were meant to be read directly against those preparations. Used for anything else, the number on the barrel is a volume measurement and nothing more.
Capacity is a separate limit from calibration
A 0.3 mL U-100 barrel holds 30 units; a 0.5 mL U-100 barrel holds 50. Arithmetic that produces 40 units is correct and undeliverable on the first of those, and a calculator that prints the number without the capacity check has answered a question the device cannot act on. The daggers in the table above mark exactly those cases.
Graduations set the real precision
Every barrel listed here is marked every single unit. That, not the arithmetic, is the limit on how finely a volume can be measured: 7.14 units is a correct calculation and an unreadable instruction on a barrel marked in whole units. Graduations and readability works through what that costs at each volume.