Water grams to cups
To convert grams to cups, divide the grams by 240. For example, 100 g of water ≈ 0.42 cup.
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Water is the one ingredient where grams and milliliters line up almost perfectly: 1 gram equals roughly 1 mL at room temperature. A US cup holds 240 grams, making water the reference point every other ingredient's density is measured against.
Water grams to cups chart (US cup)
| Grams | Cups (approx.) | Decimal cups |
|---|---|---|
| 25 g | ⅛ cup | 0.1 |
| 50 g | 0.21 cup | 0.21 |
| 75 g | ⅓ cup | 0.31 |
| 100 g | 0.42 cup | 0.42 |
| 125 g | ½ cup | 0.52 |
| 150 g | 0.62 cup | 0.62 |
| 175 g | ¾ cup | 0.73 |
| 200 g | 0.83 cup | 0.83 |
| 250 g | 1 cup | 1.04 |
| 300 g | 1¼ cups | 1.25 |
| 400 g | 1⅔ cups | 1.67 |
| 500 g | 2.08 cups | 2.08 |
Why water weighs what it does
Water defines a density of essentially 1 g/mL, which is exactly why a 240 mL US cup weighs about 240 grams. That figure shifts slightly with temperature: cold water near 4 degrees C is densest, while hot or boiling water expands and weighs a touch less per cup. The differences are tiny for baking, but they explain why a kettle-warm cup measured by weight can read a gram or two under a cold one. Mineral content in hard tap water nudges it fractionally heavier, though never enough to matter in a recipe.
How to measure water
Because water is a liquid, weigh it or use a liquid measuring cup read at eye level, never a dry cup leveled with a knife. On a scale, 240 grams is the cleanest route: tare your bowl, pour to the number, done. Surface tension can create a slight meniscus, so read the bottom of the curve at the line.
Common mistake
The classic error is assuming a US cup of water is 250 grams because that is the metric/Australian cup (250 mL). The US customary cup is 240 mL, so it weighs 240 grams. Mixing the two standards in one recipe quietly throws hydration off by about 4 percent.
Other cup sizes
| Cup type | 1 cup of water |
|---|---|
| US cup (240 ml) | 240 g |
| Metric cup (250 ml) | 250 g |
| Australian / South African cup (250 ml) | 250 g |
| Imperial cup (284 ml) | 284 g |
Where it matters
Water hydration is decisive in bread, pizza, and lean doughs, where bakers track baker's percentages to the gram. In enriched doughs, custards, and syrups, precise water weight controls texture and set. When water content shifts, dough slack, crumb openness, and crust all change, so weighing beats eyeballing every time.
FAQ
Is a cup of water 240 or 250 grams?
A US customary cup of water is 240 grams, since the US cup is 240 mL and water weighs about 1 gram per mL. The 250-gram figure comes from the 250 mL metric cup used in Australia and parts of Europe.
Does 1 gram of water really equal 1 mL?
Effectively yes, at typical room temperature. Water's density is so close to 1 g/mL that bakers treat grams and milliliters as interchangeable for water without any practical loss of accuracy.
Does water temperature change how much a cup weighs?
Slightly. Water expands as it warms, so a cup of hot water weighs marginally less than a cup of cold water. The gap is only a gram or two per cup and rarely affects a recipe.
Why do bakers weigh water instead of measuring by volume?
Weighing is faster and more repeatable, and it lets you track hydration as a baker's percentage. Taring a bowl and pouring to 240 grams removes meniscus-reading errors entirely.