Reverse dose calculator
Free calculator, no sign-up
Already drew some units? Convert syringe units back to milligrams.
Enter your numbers
Arithmetic on the numbers you enter. Check the result against your pharmacy label and ask your prescriber. Reko does not suggest doses, and this is not medical advice.
How it works
Milligrams = units ÷ 100 × concentration. A way to check what you actually drew.
- Volume (mL) = units ÷ 100.
- Dose (mg) = volume × concentration (mg/mL).
Check it against your label
- The concentration on the vial you actually used.
- That the syringe is U-100.
- That the result matches a dose your prescriber gave you.
Frequently asked questions
In short
- Milligrams = units ÷ 100 × concentration.
- The answer is only as good as the concentration you enter.
- If the result looks very different from what you meant, stop and check before anything else.
- Mixing up mg and mcg is a 1,000-fold error.
When do I need this?
When you want to know what a past draw was, or you switched vials and are not sure.
Is the result exact?
It is exact arithmetic on what you typed. The syringe itself is only as exact as its markings.
What if I do not know the concentration?
Do not guess. Ask the pharmacy or look at the label.
What does this tool do?
This tool takes the units you drew and the strength of the vial, and gives the milligrams. It is for checking a dose that has already been drawn, or for understanding an old log entry.
A worked example
Example. These numbers are made up to show the steps. They are not a label value and not a suggestion.
Made-up: 30 units drawn from a vial at 10 mg/mL.
- 30 ÷ 100 = 0.3 mL.
- 0.3 × 10 = 3 mg.
Related pages
How Reko does this in the app
Reko stores doses in milligrams. If you drew units and want to know the amount, use the reverse calculator and log the result. You can correct any dose on any date later.
Reko records what you and your prescriber decide. It never suggests a dose, and this page is not medical advice.