To convert grams of peanut butter into fluid ounces, multiply by 0.031007752: one gram comes to 0.031007752 fluid ounces. Every ingredient has its own figure here, because the units are measuring different things and only the density links them.
Water is the yardstick: 1 mL of it weighs 1 g. Peanut butter comes in at 1.0905 g per mL, or 109.1% of water, which is why a cup of it is 258 g rather than 236.6 g. Volume and weight only line up for water, and only in metric.
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 peanut butter weighs 1.138 oz, so the two readings differ by 13.8% — 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 0.388% of a cup of peanut butter, so weighing gets an accuracy no measuring cup can reach. A 500 g pack of it is 1.938 cups, and a 1 kg pack 3.876.
How the figure is arrived at: Smooth, at room temperature. Straight from the fridge it is far harder to level into a cup, and that shows up on the scale.
The formula
grams- The amount of peanut butter you are converting, in grams
0.031007751938- Fluid Ounces per gram for peanut butter, from its density of 1.0905 g/mL
fluid ounces- The equivalent quantity in fluid ounces
How it works, step by step
- Enter the quantity in grams.
- It is multiplied by 0.031007751938, the fluid ounces-per-gram figure for peanut butter.
- The result appears in fluid ounces, with a second reading in mL beneath it.
- Use the measure table if you want a standard recipe quantity rather than a number you type in.
Worked examples
50 g of peanut butter in fluid ounces
Take 50 g of peanut butter: 50 × 0.031007752 gives 1.55039 fluid ounces. Doubling the batch takes it to 3.10078 fluid ounces, because the relationship is a straight proportion once the density is known.
150 g of peanut butter in fluid ounces
A recipe calling for 150 g of peanut butter needs 4.65116 fluid ounces on the scale. The arithmetic is 150 × 0.031007752 = 4.6511628, and halving the recipe halves the weight to 2.32558 fluid ounces.
500 g of peanut butter in fluid ounces
A recipe calling for 500 g of peanut butter needs 15.5039 fluid ounces on the scale. The arithmetic is 500 × 0.031007752 = 15.503876, and halving the recipe halves the weight to 7.75194 fluid ounces.
How to read your score
Frequently asked questions
How many fluid ounces are in 1 g of peanut butter?
One gram of peanut butter is 0.031007752 fluid ounces. Half that quantity is 0.0155039 fluid ounces and double it is 0.0620155 fluid ounces, so the figure scales straight up and down — there is no offset in this conversion, only the factor.
Why is a cup of peanut butter not 236 g like water?
Because weight per cup depends on what is in the cup. Peanut butter has a density of 1.0905 g per mL where water has 1.00, so a cup of it weighs 258 g rather than 236.6 g. That is a difference of 21.4 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. Peanut butter does not compress, so a cup of it is 258 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 peanut butter 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 peanut butter weighs 1.138 oz, so the two readings differ by 13.8%. 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 peanut butter would weigh 272.63 g instead of 258 g — 14.6 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 peanut butter — roughly 2.58 g on a 258 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 much does 3 fl oz of peanut butter weigh?
3 fl oz of peanut butter comes to 96.75 g, or 96.75 grams. This page runs that calculation in reverse — enter a weight and it returns the volume — and the fluid-ounces-to-grams page does it in the direction the question is usually asked.
Peanut butter in grams and fluid ounces
| Grams | Fluid Ounces | Unrounded |
|---|---|---|
| 5 g | 0.155039 fl oz | 0.1550387597 |
| 10 g | 0.310078 fl oz | 0.3100775194 |
| 25 g | 0.775194 fl oz | 0.7751937984 |
| 50 g | 1.55039 fl oz | 1.550387597 |
| 100 g | 3.10078 fl oz | 3.100775194 |
| 125 g | 3.87597 fl oz | 3.875968992 |
| 150 g | 4.65116 fl oz | 4.651162791 |
| 200 g | 6.20155 fl oz | 6.201550388 |
| 250 g | 7.75194 fl oz | 7.751937984 |
| 300 g | 9.30233 fl oz | 9.302325581 |
| 500 g | 15.5039 fl oz | 15.50387597 |
| 1000 g | 31.0078 fl oz | 31.00775194 |
Based on 258 g per cup of peanut butter. One gram of peanut butter is 0.031007752 fluid ounces.
| Measure | Grams | Ounces | Millilitres |
|---|---|---|---|
| 1 cup | 258 g | 9.1 oz | 236.6 mL |
| 3/4 cup | 193.5 g | 6.83 oz | 177.4 mL |
| 2/3 cup | 172 g | 6.07 oz | 157.7 mL |
| 1/2 cup | 129 g | 4.55 oz | 118.3 mL |
| 1/3 cup | 86 g | 3.03 oz | 78.86 mL |
| 1/4 cup | 64.5 g | 2.28 oz | 59.15 mL |
| 1 tbsp | 16.12 g | 0.569 oz | 14.79 mL |
| 1 tsp | 5.375 g | 0.19 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) |
|---|---|---|---|
| Tomato sauce | 245 g | 8.642 oz | 1.036 |
| Orange juice | 248 g | 8.748 oz | 1.048 |
| Evaporated milk | 252 g | 8.889 oz | 1.065 |
| Peanut butter (this page) | 258 g | 9.101 oz | 1.091 |
| Sweetened condensed milk | 306 g | 10.79 oz | 1.293 |
| Maple syrup | 322 g | 11.36 oz | 1.361 |
| Corn syrup | 328 g | 11.57 oz | 1.386 |
Ordered by weight. The spread across this group is why a single generic cups-to-grams factor cannot work.