Fluid Ounces of water to grams runs on one number, 29.5 grams per fluid ounce. It is a measured property of this ingredient rather than a defined conversion, which is why a generic volume-to-weight tool cannot give you it.
The density behind that figure is 0.99751 g per mL, against 1.00 for water. A cup of water weighs 236.6 g and a cup of water weighs 236 g, so this ingredient is 99.75% as heavy as the same volume of water — the single fact the whole page rests on.
This is the pair that catches people out. A fluid ounce is a volume and an ounce is a weight, and they are only the same number for something with the density of water. One fluid ounce of water weighs 1.041 oz, so the two readings differ by 4.06% — worth knowing before trusting a recipe that just says "oz".
Grams are the unit this conversion is really for. A domestic scale resolves to a gram, which is 0.424% of a cup of water, so weighing gets an accuracy no measuring cup can reach. A 500 g pack of it is 2.119 cups, and a 1 kg pack 4.237.
The condition this weight assumes: The reference case. A US cup is 236.6 mL and water is 1 g per mL, so the two numbers are the same and every other ingredient can be read against it.
The formula
fluid ounces- The amount of water you are converting, in fluid ounces
29.5- Grams per fluid ounce for water, from its density of 0.99751 g/mL
grams- The equivalent quantity in grams
How it works, step by step
- Enter the quantity in fluid ounces.
- It is multiplied by 29.5, the grams-per-fluid ounce figure for water.
- The result appears in grams, with a second reading in oz beneath it.
- Use the measure table if you want a standard recipe quantity rather than a number you type in.
Worked examples
3 fl oz of water in grams
Take 3 fl oz of water: 3 × 29.5 gives 88.5 grams. Doubling the batch takes it to 177 grams, because the relationship is a straight proportion once the density is known.
6 fl oz of water in grams
Take 6 fl oz of water: 6 × 29.5 gives 177 grams. Doubling the batch takes it to 354 grams, because the relationship is a straight proportion once the density is known.
12 fl oz of water in grams
12 fl oz of water weighs out at 354 grams. Divide 354 by 29.5 and you get back to 12 fl oz, which is the quickest check that the factor is the right way up.
How to read your score
Frequently asked questions
How many grams are in 1 fl oz of water?
One fluid ounce of water is 29.5 grams. Half that quantity is 14.75 grams and double it is 59 grams, so the figure scales straight up and down — there is no offset in this conversion, only the factor.
Why is a cup of water not 236 g like water?
Because weight per cup depends on what is in the cup. Water has a density of 0.99751 g per mL where water has 1.00, so a cup of it weighs 236 g rather than 236.6 g. That is a difference of 0.6 g per cup, and it is the reason a single volume-to-weight factor cannot be applied to every ingredient.
Does how I measure it change the weight?
Barely. Water does not compress, so a cup of it is 236 g however it is poured — within about 1%, which is inside the accuracy of a domestic scale. This is the group where measuring by volume is defensible.
Is a fluid ounce of water the same as an ounce?
No. A fluid ounce is a volume — one eighth of a US cup, 29.57 mL — and an ounce is a weight. One fluid ounce of water weighs 1.041 oz, so the two readings differ by 4.06%. They coincide only for something with the density of water, and then only roughly.
Is this a US cup or a metric cup?
US customary: 236.59 mL, which is the cup every US recipe means. A metric cup is 250 mL, so the same cup of water would weigh 249.38 g instead of 236 g — 13.4 g more, or 5.67%. Australian and some European recipes use the metric cup, and the difference is large enough to matter in baking.
Do I need a scale for this, or will measuring cups do?
A scale, if the result matters. Volume measuring carries a spread of about 1% for water — roughly 2.36 g on a 236 g cup — while a domestic scale is accurate to a gram or two. For anything where the ratio of ingredients drives the outcome, bread and pastry above all, weigh it.
How many fluid ounces of water is 500 g?
500 g of water is 16.949 fluid ounces — 0.0338983 fluid ounces to one gram, so 500 × 0.0338983 = 16.949. Going that way is a division by 29.5, or a multiplication by 0.0338983 if you prefer.
Water in fluid ounces and grams
| Fluid Ounces | Grams | Unrounded |
|---|---|---|
| 1 fl oz | 29.5 g | 29.5 |
| 2 fl oz | 59 g | 59 |
| 3 fl oz | 88.5 g | 88.5 |
| 4 fl oz | 118 g | 118 |
| 6 fl oz | 177 g | 177 |
| 8 fl oz | 236 g | 236 |
| 12 fl oz | 354 g | 354 |
| 16 fl oz | 472 g | 472 |
Based on 236 g per cup of water. One fluid ounce of water is 29.5 grams.
| Measure | Grams | Ounces | Millilitres |
|---|---|---|---|
| 1 cup | 236 g | 8.32 oz | 236.6 mL |
| 3/4 cup | 177 g | 6.24 oz | 177.4 mL |
| 2/3 cup | 157.3 g | 5.55 oz | 157.7 mL |
| 1/2 cup | 118 g | 4.16 oz | 118.3 mL |
| 1/3 cup | 78.67 g | 2.77 oz | 78.86 mL |
| 1/4 cup | 59 g | 2.08 oz | 59.15 mL |
| 1 tbsp | 14.75 g | 0.52 oz | 14.79 mL |
| 1 tsp | 4.917 g | 0.173 oz | 4.929 mL |
US customary measures: 1 cup = 236.59 mL, 1 tbsp = 14.79 mL, 1 tsp = 4.93 mL.
| Ingredient | Grams per cup | Ounces per cup | Density (g/mL) |
|---|---|---|---|
| Coconut oil | 218 g | 7.69 oz | 0.9214 |
| Mayonnaise | 220 g | 7.76 oz | 0.9299 |
| Cream cheese | 227 g | 8.007 oz | 0.9595 |
| Water (this page) | 236 g | 8.325 oz | 0.9975 |
| Heavy cream | 238 g | 8.395 oz | 1.006 |
| Vinegar | 239 g | 8.43 oz | 1.01 |
| Sour cream | 240 g | 8.466 oz | 1.014 |
Ordered by weight. The spread across this group is why a single generic cups-to-grams factor cannot work.