mg to ml Converter
Convert milligrams to millilitres, or back again, using the concentration on a label or the density of the liquid.
Medicine label "250 mg / 5 ml" = 50 mg per ml. Water has a density of 1 g per ml, so 1000 mg of water = 1 ml.
Why mg to ml needs a concentration
Milligrams (mg) measure mass: how much stuff there is. Millilitres (ml) measure volume: how much space it takes up. They are different kinds of quantity, so there is no single number that converts one into the other. A millilitre of water, of honey and of a medicine all weigh different amounts.
The link between them is the concentration (for a solution, such as a liquid medicine) or the density (for a pure liquid). Concentration says how many mg of the active ingredient are dissolved in each ml; density says how many grams each ml of the liquid itself weighs. Once you know one of these, converting is a single division or multiplication.
Only for water, at 1 g per ml, is 1 ml the same as 1000 mg. That shortcut is often used by mistake for other liquids, and for medicines it can give a dose many times too big or too small.
The mg to ml formula
- ml = mg ÷ concentration (concentration in mg per ml)
- mg = ml × concentration
- With a density in g/ml: ml = mg ÷ (density × 1000)
Exemple résolu
A syrup label says 250 mg in 5 ml, so the concentration is 250 ÷ 5 = 50 mg/ml. A 400 mg dose is 400 ÷ 50 = 8 ml.
Always follow the dose on a medicine’s label or from a pharmacist; this converter is for checking the arithmetic.
More conversions like this, with every formula worked through, are in the Formules de chimie calculator, and molar masses in the Molar Mass Calculator.
Foire aux questions
How many mg are in 1 ml?
It depends on the liquid. For water (density 1 g/ml), 1 ml weighs 1000 mg. For a medicine, the label tells you: "250 mg / 5 ml" means 50 mg in every 1 ml.
How do I convert mg to ml?
Divide the mass in mg by the concentration in mg per ml. 500 mg of a 50 mg/ml liquid is 500 ÷ 50 = 10 ml.
How do I convert ml to mg?
Multiply the volume in ml by the concentration in mg per ml. 5 ml of a 50 mg/ml liquid contains 5 × 50 = 250 mg.
Why can’t mg be converted to ml directly?
Milligrams measure mass and millilitres measure volume. You need to know how much mass fits in each ml (the concentration or density) to go from one to the other.
