Milligrams to Milliliters Converter
Milligrams measure weight and milliliters measure volume, so the answer depends on the liquid's density. For water, 1,000 mg is about 1 mL.
Sources: USGS, NIST SP 811 Updated
Not for medicine. This page converts the weight of a liquid to its volume using density. A dose in mg is the amount of active ingredient, which depends on the strength printed on the label (for example 250 mg per 5 mL), not on density. Do not use this converter to measure a dose.
Result
500 mg = 0.5 mL
at a density of 1 g/mL
The formula
mL = mg ÷ (density in g/mL × 1,000)
Density says how much one milliliter of the liquid weighs. A density of 1 g/mL means 1 mL weighs 1 gram, which is 1,000 mg. Going the other way, mg = mL × density × 1,000.
Water is the usual reference. Its density is 0.99802 g/mL at 21 °C according to the U.S. Geological Survey, which is why 1 g/mL is used as a round figure. Other liquids can be well above or below that, and using 1 for them gives the wrong volume.
Worked example
- Water, density 1 g/mL: 500 mg ÷ (1 × 1,000) = 0.5 mL.
- A liquid with a density of 1.25 g/mL: 500 mg ÷ (1.25 × 1,000) = 0.4 mL. Denser liquid, less volume for the same weight.
- A liquid with a density of 0.8 g/mL: 500 mg ÷ (0.8 × 1,000) = 0.625 mL.
Milligrams in a milliliter at different densities
| Density (g/mL) | 1 mL weighs | 1,000 mg takes up |
|---|---|---|
| 0.7 | 700 mg | 1.429 mL |
| 0.8 | 800 mg | 1.25 mL |
| 0.9 | 900 mg | 1.111 mL |
| 1 | 1000 mg | 1 mL |
| 1.1 | 1100 mg | 0.909 mL |
| 1.2 | 1200 mg | 0.833 mL |
| 1.3 | 1300 mg | 0.769 mL |
| 1.4 | 1400 mg | 0.714 mL |
| 1.5 | 1500 mg | 0.667 mL |
Frequently asked questions
How many mg are in 1 mL?
It depends on the liquid. For water it is about 1,000 mg (998 mg at room temperature). For a liquid with a density of 0.8 g/mL it is 800 mg, and for one with 1.4 g/mL it is 1,400 mg. Multiply the density in g/mL by 1,000.
Is 1 mg the same as 1 mL?
No. A milligram is a weight and a milliliter is a volume. One milliliter of water weighs about a gram, which is 1,000 milligrams, so the two numbers differ by a factor of about a thousand even for water.
Can I use this to work out a dose of medicine?
No. The milligrams on a medicine label are the amount of active ingredient, not the weight of the liquid. The label states a strength, such as 250 mg in 5 mL, and that strength is what links the dose to the volume. It has nothing to do with the liquid's density. Follow the label, or ask a pharmacist or doctor.
Where do I find the density of a liquid?
On the product's technical or safety data sheet, usually in g/mL, g/cm³ or kg/L, which are all the same number. Density changes a little with temperature, so use the figure for the temperature you are working at.
Sources
- U.S. Geological Survey, Water Science School: Water Density — water is 0.99802 g/cm³ at 70 °F (21 °C); 1 g/mL is the usual rounding (checked October 12, 2026)
- NIST Special Publication 811, Appendix B.8 — 1 g/cm³ = 1,000 kg/m³; 1 mL = 1 cm³ (checked October 12, 2026)