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mg to mL Converter

Updated July 2026 · Written & fact-checked by the NumberBench editorial team · How we calculate

Milligrams measure mass; milliliters measure volume. Pick what you're measuring (or enter a medicine's mg/mL concentration) and this tool does the density math for you.

Example: with Amount (mg) 500 · Substance Water (1 g/mL) · Custom density (g/mL) 1 → Volume: 0.50 mL.

Computed by the calculator below using its default values. Change any input to see your own numbers.

Volume—
In US teaspoons—
Steps—
📊 Benchmark: water has a density of 1 g/mL at 4°C, so 1,000 mg of water = exactly 1 mL — other liquids need their own density. NIST / USP.

💊 Track meds & doses with a pill organizer

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Why mg to mL needs a density

A milligram is mass and a milliliter is volume, so there is no universal conversion — you always divide by the substance’s density. For water it’s simple: 1 mL of water weighs 1,000 mg, so 500 mg of water = 0.5 mL. Denser liquids like honey pack more milligrams into each milliliter (500 mg of honey is only about 0.35 mL), while oils go the other way.

For liquid medicine, skip density and use the concentration printed on the label. Convert it to g/mL and enter it with the “custom” option: a children’s syrup at 160 mg per 5 mL is 32 mg/mL, i.e. 0.032 g/mL. A 100 mg dose at that strength works out to 3.13 mL — just over half a teaspoon.

How it’s calculated

Volume (mL) = mass (mg) ÷ (density in g/mL × 1,000). The substance list uses standard reference densities (water 1.00, milk 1.03, cooking oil 0.92, honey 1.42 g/mL); the custom option accepts any density or mg/mL concentration expressed in g/mL. Teaspoons use the US definition: 1 tsp = 4.92892 mL.

Results update as you type and are estimates, not professional advice — verify important decisions with a qualified professional.

Common mistakes

  • Assuming 1 mg = 1 mL for every liquid — that only holds for water, and only approximately for milk.
  • Using density for medicines instead of the labeled concentration (mg per mL) — they are different numbers.
  • Mixing up mg (mass) with mL (volume) on dosing instructions.

Frequently asked questions

Is 1 mg equal to 1 mL?

No. For water, 1 mL weighs 1,000 mg, so 1 mg of water is 0.001 mL. Milligrams only equal milliliters after dividing by the liquid's density.

How do I convert mg to mL for medicine?

Use the concentration on the label, not density. Divide the dose in mg by the mg/mL strength: a 200 mg dose of a 40 mg/mL liquid is 200 ÷ 40 = 5 mL.

How many mL is 500 mg of water?

500 ÷ 1,000 = 0.5 mL, because water's density is 1 g/mL. The same 500 mg of honey is only about 0.35 mL, since honey is denser.

What is the general mg to mL formula?

mL = mg ÷ (density in g/mL × 1,000). Multiply the other way (mL × density × 1,000) to go from milliliters back to milligrams.