Injection dose calculator: turn mg into mL and units
Short answer: If your vial already has a strength on the label, such as 5 mg/mL or 200 mg/mL, the volume you need is your prescribed dose divided by that strength. Multiply the millilitres by 100 for units on a U-100 insulin syringe. The calculator below does it, and can count how many doses the vial holds.
How the calculation works
Volume (mL) = prescribed dose (mg) ÷ strength (mg/mL). Units on a U-100 syringe are that volume × 100.
Worked examples with made-up numbers:
- A single-dose vial labelled 5 mg in 0.5 mL is 10 mg/mL. A prescribed 5 mg is the whole 0.5 mL.
- A multi-dose vial at 200 mg/mL with a prescribed 100 mg is 100 ÷ 200 = 0.5 mL.
- A compounded vial labelled 2.5 mg/mL with a prescribed 1 mg is 0.4 mL, or 40 units on a U-100 syringe.
Things to check on the label
- Strength per mL, not per vial. A label can say "10 mg/2 mL". That is 5 mg/mL.
- Single-dose or multi-dose. Single-dose vials such as Zepbound vials are meant to be used once, whatever is left in them.
- Syringe and needle. Oil-based injections such as testosterone are often drawn up and given with different needles. Your clinic will tell you which to use.
If the answer does not match what your pharmacist or clinic showed you, trust them and ask why before injecting.
Let the app keep doing this
A web calculator forgets your vial the moment you close the tab. In PepLevel you save each vial or pen once: how much it holds and how much water went in, or the strength on the label. From then on, every planned dose from your prescriber's plan shows its volume in mL (cc in the US), and in syringe units if you enter the scale, on Today, on the medication page and when you log the dose. The app also tracks what is left in the vial and reminds you before you run out. Like this page, it only converts the dose you were given. It never works out what your dose should be.
Common questions
How do I calculate mL from mg?
Divide the dose in mg by the strength of the liquid in mg per mL. For example, 100 mg from a 200 mg/mL vial is 0.5 mL.
How many units is 0.5 mL?
On a U-100 insulin syringe, 0.5 mL is 50 units. Other syringe scales differ, so check the markings on yours.
Can I use this for a Zepbound or testosterone vial?
Yes, for the arithmetic. Enter the strength from the label and the dose on your prescription. Always follow the product instructions and your prescriber for how to draw up and inject.
PepLevel does this from your own doses
Saved vials, planned doses in mL, and a level curve built from what you actually logged. Coming soon to the App Store.
Get PepLevelMedical disclaimer: this tool does arithmetic and illustrative estimates only. It is not medical advice, does not recommend any dose and is not a substitute for your prescriber, pharmacist or the product information. PepLevel is a logging and reminder tool only.