To convert cups of peanut butter into ounces, multiply by 9.1006822: one cup comes to 9.1006822 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.
A cup of peanut butter is 258 g when it is measured the standard way, but how it gets into the cup changes the answer: between about 256.7 g and 260.6 g covers the range from lightly spooned to firmly packed. That 1% spread is larger than most of the adjustments recipes fuss over, and it disappears entirely the moment the ingredient is weighed instead.
One cup of peanut butter is 9.101 oz. US kitchen scales usually step in eighths of an ounce, which is 3.54 g — around 1.37% of a cup of this ingredient, so the scale is precise enough for a full cup and coarse for a spoonful. That is why recipes mix the two systems: ounces for the bulk, spoons for the small amounts.
What the number depends on: 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
cups- The amount of peanut butter you are converting, in cups
9.10068218299- Ounces per cup for peanut butter, from its density of 1.0905 g/mL
ounces- The equivalent quantity in ounces
How it works, step by step
- Enter the quantity in cups.
- It is multiplied by 9.10068218299, the ounces-per-cup figure for peanut butter.
- The result appears in ounces, with a second reading in g beneath it.
- Use the measure table if you want a standard recipe quantity rather than a number you type in.
Worked examples
1/3 cup of peanut butter in ounces
1/3 cup of peanut butter weighs out at 3.03356 ounces. Divide 3.03356 by 9.1006822 and you get back to 1/3 cup, which is the quickest check that the factor is the right way up.
3/4 cup of peanut butter in ounces
A recipe calling for 3/4 cup of peanut butter needs 6.82551 ounces on the scale. The arithmetic is 0.75 × 9.1006822 = 6.8255116, and halving the recipe halves the weight to 3.41276 ounces.
3 cup of peanut butter in ounces
Take 3 cup of peanut butter: 3 × 9.1006822 gives 27.302 ounces. Doubling the batch takes it to 54.6041 ounces, because the relationship is a straight proportion once the density is known.
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Frequently asked questions
How many ounces are in 1 cup of peanut butter?
One cup of peanut butter is 9.1006822 ounces. Half that quantity is 4.55034 ounces and double it is 18.2014 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 many cups of peanut butter is 16 oz?
16 oz of peanut butter is 1.7581 cups — 0.109882 cups to one ounce, so 16 × 0.109882 = 1.7581. Going that way is a division by 9.10068, or a multiplication by 0.109882 if you prefer.
Peanut butter in cups and ounces
| Cups | Ounces | Unrounded |
|---|---|---|
| 1/8 cup | 1.13759 oz | 1.137585273 |
| 1/4 cup | 2.27517 oz | 2.275170546 |
| 1/3 cup | 3.03356 oz | 3.033560728 |
| 1/2 cup | 4.55034 oz | 4.550341091 |
| 2/3 cup | 6.06712 oz | 6.067121455 |
| 3/4 cup | 6.82551 oz | 6.825511637 |
| 1 cup | 9.10068 oz | 9.100682183 |
| 1 1/2 cup | 13.651 oz | 13.65102327 |
| 2 cup | 18.2014 oz | 18.20136437 |
| 3 cup | 27.302 oz | 27.30204655 |
| 4 cup | 36.4027 oz | 36.40272873 |
Based on 258 g per cup of peanut butter. One cup of peanut butter is 9.1006822 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.