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Convert a measured volume of water from milliliters into US cups, metric cups, US fluid ounces and liters. The tool also estimates water mass in grams using a density close to 0.998 g/mL at 20 °C. This is useful when a recipe gives a liquid volume but your kitchen scale measures mass.
Water measurement converter
Results are estimates based on the values you enter. Nothing you type is sent to or stored on our servers.
Conversion model
The converter treats volume and mass as different physical quantities. For US cups, it divides milliliters by 236.588; for metric cups, it divides by 250; for US fluid ounces, it divides by 29.5735; and for liters, it divides by 1,000. The approximate water mass is calculated as mass (g) = volume (mL) × 0.998.
A US customary cup is about 236.588 mL, while a metric cup is 250 mL. These are not interchangeable. The distinction matters when scaling a recipe or converting instructions from another country.
Worked examples
For 250 mL of water, the result is about 1.057 US cups, exactly 1 metric cup by the 250 mL convention, about 8.45 US fluid ounces and 0.25 liters. The estimated mass is about 249.5 g at the density used by the tool.
For 500 mL, the result is about 2.113 US cups, 2 metric cups, 16.91 US fluid ounces and 0.5 liters. The estimated mass is about 499 g. Small differences from a kitchen scale are expected because water density changes slightly with temperature.
How to use the result
- Enter the water volume in milliliters. Use the volume actually measured, not the capacity printed on a bottle unless it is full.
- Read the US cup and metric cup outputs separately. Choose the one that matches the recipe’s measurement system.
- Use the gram estimate only when a recipe or scale requires water mass. For most home recipes, rounding to the nearest gram is sufficient.
Accuracy and limitations
The mass estimate assumes pure water near 20 °C. Water density is not exactly 1.000 g/mL at every temperature, and dissolved salt, sugar or other ingredients change density. Do not apply this water-mass estimate to milk, oil, honey, syrup or other liquids; use an ingredient-specific density or weigh the ingredient directly.
Measuring-cup markings and household pouring technique introduce more uncertainty than the displayed decimal places suggest. For baking or repeatable food production, a calibrated digital scale is usually more reliable than a volume estimate.
Frequently asked questions
Is 250 mL one US cup?
No. A US customary cup is about 236.588 mL. A 250 mL cup is a metric cup. The converter displays both so you can select the correct standard.
Does 1 mL of water always weigh 1 gram?
No. It is a useful approximation, but pure water is about 0.998 g/mL near 20 °C. Temperature changes density slightly.
Can I use this for oil or milk?
Use the volume outputs, but do not use the water mass estimate for other liquids. Their densities differ.
Related tools and reference
For spoon measures, use the Teaspoons to Milliliters Converter. For a reverse volume conversion, see the Milliliters to Cups Converter. Reference factors are consistent with the NIST customary-to-metric conversion guide.