FreePeptideCalc

mg to mL Converter: How Many mL Is Your Dose?

Written by , who builds and maintains this site and is not a clinician. Every figure links to its primary source.

mL = mg ÷ concentration (mg/mL). Milligrams are a mass and millilitres are a volume, so the answer depends on how much drug is in each millilitre of your solution. 2.5 mg is 1 mL at 2.5 mg/mL and 0.25 mL at 10 mg/mL — same dose, four times the volume.

Any single answer is a guess. A page that says “5 mg is 0.5 mL” has silently assumed 10 mg/mL. Use the concentration on your own label or the one you created when you added water.

Calculator inputs

Convert from your concentration

Units only mean something after the vial and water volume are known.

At 5 mg/mL

2.5 mg = 50 units0.5 mL

On a U-100 syringe, where 100 units = 1 mL.

50 units01020304050U-100 barrel · 50 units · read the leading edge of the black plunger seal
Draw to 50 units on a 50-unit U-100 syringe.

Why there is no single answer

A syringe unit measures volume, not mass: one unit is 1/100 of a millilitre. So at 2.5 mg lands on a different mark at every concentration. Find the row matching the vial and water volume you actually used.

ConcentrationExample vial + water2.5 mg is
1 mg/mL2 mg in 2 mL250 units
2 mg/mL4 mg in 2 mL125 units
2.5 mg/mL5 mg in 2 mL100 units
5 mg/mL10 mg in 2 mL50 units
10 mg/mL20 mg in 2 mL25 units
20 mg/mL40 mg in 2 mL12.5 units

The formula

mg per mL = vial mg ÷ water mL

mL = dose mg ÷ mg per mL

syringe units = mL × 100(U-100 barrel)

Worked through: a 10 mg vial with 2 mL of water is 5 mg/mL. A 2.5 mg dose is 2.5 ÷ 5 = 0.5 mL, which is 50 units on a U-100 syringe. Add 1 mL instead and the same vial is 10 mg/mL, so 2.5 mg becomes 0.25 mL — 25 units.

mg to mL at common concentrations

Find your concentration in the left column. The figure under each volume is the same draw in U-100 syringe units.

Concentration0.25 mg0.5 mg1 mg2 mg2.5 mg5 mg
2.5 mg/mL5 mg vial + 2 mL0.1 mL10 units0.2 mL20 units0.4 mL40 units0.8 mL80 units1 mL100 units2 mL200 units
5 mg/mL10 mg vial + 2 mL0.05 mL5 units0.1 mL10 units0.2 mL20 units0.4 mL40 units0.5 mL50 units1 mL100 units
6.67 mg/mL10 mg vial + 1.5 mL0.038 mL3.8 units0.075 mL7.5 units0.15 mL15 units0.3 mL30 units0.375 mL37.5 units0.75 mL75 units
10 mg/mL30 mg vial + 3 mL0.025 mL2.5 units0.05 mL5 units0.1 mL10 units0.2 mL20 units0.25 mL25 units0.5 mL50 units
12.5 mg/mL25 mg vial + 2 mL0.02 mL2 units0.04 mL4 units0.08 mL8 units0.16 mL16 units0.2 mL20 units0.4 mL40 units
15 mg/mL30 mg vial + 2 mL0.017 mL1.7 units0.033 mL3.3 units0.067 mL6.7 units0.133 mL13.3 units0.167 mL16.7 units0.333 mL33.3 units
20 mg/mL60 mg vial + 3 mL0.013 mL1.3 units0.025 mL2.5 units0.05 mL5 units0.1 mL10 units0.125 mL12.5 units0.25 mL25 units
30 mg/mL60 mg vial + 2 mL0.008 mL0.8 units0.017 mL1.7 units0.033 mL3.3 units0.067 mL6.7 units0.083 mL8.3 units0.167 mL16.7 units

Reading a label written as mg per something else

Pens and prefilled syringes often state strength per dose volume rather than per millilitre — 2.5 mg/0.5 mL, for instance. Divide the two: 2.5 ÷ 0.5 = 5 mg/mL. Do that before any other arithmetic, because putting the per-dose figure into a per-mL formula is off by exactly the ratio of the two volumes.

For a vial you reconstitute yourself, the concentration is whatever you made it. The water only sets the concentration; it does not change the milligrams in the vial. See how much bacteriostatic water to use for choosing a volume that lands your dose on a readable mark.

Related conversions

  • Units to mL — fixed, no concentration needed: 100 units = 1 mL on U-100.
  • mcg to mL — the same question for doses written in micrograms (1 mg = 1,000 mcg).
  • mg to units — pages for every common dose, from 0.25 mg to 40 mg.

Common questions

Sources

Every number on this page comes from one of the documents below. Where no reliable source exists, the page says so instead of filling the gap.

  1. GuidelineInternational Organization for Standardization· 2016-03
    ISO 8537:2016 — Sterile single-use syringes, with or without needle, for insulin (scope and requirements; full text not public)
  2. FDA labelFDA / DailyMed
    Bacteriostatic Water for Injection, USP — FDA prescribing information (NDA 018802)
  3. GuidelineFDA / CDER· 2015-06
    Guidance for Industry: Allowable Excess Volume and Labeled Vial Fill Size in Injectable Drug and Biological Products
  4. Published studyJournal of Family Medicine and Primary Care 2017;6(4):724–729· 2017
    Chowdhury S, Chakraborty PP. Errors of insulin therapy: real-life experiences from developing world