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Dose unit converter

Convert a prescribed dose between milligrams, micrograms, millilitres and U-100 syringe units for any concentration, with the nearest syringe mark for each common syringe size. Built for compounded vials where the concentration changes from fill to fill.

By FormBlends editorial teamAssumptions checked September 4, 2026 Runs in your browser; nothing is sent to a server

What it computes

mg, mcg, mL and syringe units at any vial concentration.

Never pre-fills a dose

Inputs

mg/mL

Copy it from the pharmacy label, for example 10 mg/mL or 2.5 mg/mL.

Enter the amount exactly as your prescriber wrote it, then choose its unit.

Result

Enter a concentration and a dose. Nothing is pre-filled on purpose: the numbers must come from your prescription and your vial label.

Formula
concentration (mg/mL) = total mg in vial / total mL in vial
volume (mL)           = dose (mg) / concentration (mg/mL)
syringe units (U-100) = volume (mL) x 100
dose (mg)             = syringe units / 100 x concentration (mg/mL)
micrograms            = milligrams x 1000

Worked example: a 10 mg vial made up to 1 mL is 10 mg/mL. A prescribed 2.5 mg dose is 2.5 / 10 = 0.25 mL, which is 25 units on a U-100 syringe. The same prescription from a 5 mg/mL vial would be 0.5 mL, or 50 units. The dose did not change; the volume did.

Assumptions, checked September 4, 2026
  • Syringe units are U-100 insulin-syringe graduations: 100 units per 1 mL, so 1 unit = 0.01 mL. If your syringe is not U-100, do not use the units figure.
  • The concentration is taken exactly as you typed it. Compounded vials vary between pharmacies and between fills; read every new vial label.
  • Syringe graduations: 0.3 mL syringes are marked in half units, 0.5 mL in single units, 1 mL in 2-unit steps. Rounding is shown to the nearest mark.
  • Compounded semaglutide and tirzepatide are not FDA approved and are not interchangeable with brand pens, whose doses are set by the pen, not by a syringe.

This calculator is an arithmetic aid for medication a licensed prescriber has already prescribed. It does not recommend a dose. Confirm any result with your prescriber or pharmacist before use.

Sources

  1. ISMP Guidelines for Optimizing Safe Subcutaneous Insulin Use in Adults (U-100 syringe graduations and unit/volume confusion)
  2. FDA: Human Drug Compounding (overview of 503A and 503B, and the statement that compounded drugs are not FDA approved)

Read before you use it

Guides for this calculator

Paper-cut illustration of a syringe with plain tick marks beside a slide rule and a ruler

How to use the dose unit converter

You'll get: The converter turns the dose on your prescription and the strength on your vial into millilitres and syringe units.

A walkthrough of the converter: what to type, what each result means, and the two checks that catch almost every drawing-up error before it happens.

Updated September 4, 2026

Educational, not medical advice. Read the medical disclaimer.