Convert water between grams and cups using US customary, US legal, metric, or imperial cup sizes, with milliliter, ounce, and fraction-cup results.
Grams to Cups of Water Formula
- cups — volume in US cups
- grams — mass of water in grams
- 236.5882 — milliliters in one US cup
This calculator approximates water density as 1 g/mL for kitchen conversions, so grams estimate the same numerical volume in milliliters. It uses 236.5882365 mL per US customary cup, 240 mL per US nutrition-labeling cup, 250 mL per metric cup, and 284.130625 mL for the retained imperial half-pint convention. These mass-to-volume answers are approximate; actual density varies with temperature and dissolved substances.
Quick Reference Tables
Approximate conversions for water using the calculator’s 1 g/mL density assumption:
| Grams | US Cups | Metric Cups | ml |
|---|---|---|---|
| 50 g | 0.211 | 0.2 | 50 |
| 100 g | 0.423 | 0.4 | 100 |
| 150 g | 0.634 | 0.6 | 150 |
| 200 g | 0.845 | 0.8 | 200 |
| 237 g | 1.002 | 0.948 | 237 |
| 250 g | 1.057 | 1.000 | 250 |
| 500 g | 2.113 | 2.0 | 500 |
| 1000 g | 4.227 | 4.0 | 1000 |
Use the cup definition specified by your recipe. NIST’s customary tables define a US measuring cup as 8 US fluid ounces. FDA nutrition-labeling guidance uses 240 mL. FSANZ’s water methodology uses a 250 mL cup with a 1 g/mL density assumption. The imperial option is a half-pint convention based on the 4.54609 L imperial gallon.
| Cup Type | ml per cup | Used in |
|---|---|---|
| US legal cup | 240 | US nutrition labels |
| US customary cup | 236.5882 | US recipes |
| Metric cup | 250 | Recipes specifying a 250 mL cup |
| UK imperial cup | 284.131 | Half an imperial pint; confirm the recipe’s convention |
Worked Example and FAQ
Example: A recipe calls for 180 g of water. 180 ÷ 236.5882 = 0.761 US cups, or about 3/4 cup.
Is 250 g of water 1 cup? It is approximately 1 metric cup using the calculator’s 1 g/mL water-density assumption. In US customary cups, 250 g is approximately 1.057 cups. Check which cup your recipe specifies.
Why does this only work for water? The shortcut grams ≈ mL uses an approximate water density of 1 g/mL. Flour, sugar, oil, and milk have different densities, so the same gram value gives a different cup volume.
Does temperature matter? Yes. Water density changes with temperature. The USGS density table gives about 0.99802 g/mL at 21°C and 0.95865 g/mL at 100°C. Hot water therefore occupies more volume for the same mass. This calculator retains the simple 1 g/mL kitchen approximation rather than correcting for temperature.
