How we calculate and check every number

Exact definitions

• 1 US fluid ounce = 29.5735295625 mL (exact).
• 1 US cup = 8 US fl oz = 236.5882365 mL; 1 Tbsp = 1/2 fl oz; 1 tsp = 1/6 fl oz.
• 1 pint = 16 fl oz; 1 quart = 32 fl oz; 1 gallon = 128 fl oz.
• 1 ounce (avoirdupois, weight) = 28.349523125 g; 1 lb = 453.59237 g.
• 1 imperial (UK) fl oz = 28.4130625 mL.

Source: NIST Handbook 44 and NIST SP 811.

Three different “cups”

• US customary cup, used in US recipes and measuring cups: 236.59 mL. This is the default everywhere on the site.
• US nutrition-label cup: 240 mL, set by the FDA for food labels (21 CFR 101.9).
• Metric cup: 250 mL, used in recipes from Australia, Canada, New Zealand and the UK.

Rounding

• All math is done at full precision; rounding happens only when a number is shown.
• Fluid ounces and tablespoons: up to 2 decimals. Milliliters: whole numbers from 10 mL up, 1 decimal below.
• Cups are shown as the nearest fraction you can measure (halves, thirds, quarters, eighths). When the fraction is not exact, it is marked with “≈” or “about”, and the decimal is shown too.
• Kitchen fractions are computed in units of 1/8 teaspoon, so 1/3 cup, 1/6 cup and 3/8 cup are exact.

“Measure with” suggestions

The tool finds the fewest scoops from a standard US set (1, 1/2, 1/3 and 1/4 cup; 1 Tbsp, 1 tsp, 1/2, 1/4 and 1/8 tsp) that add up to the amount exactly. When an amount is not a whole number of 1/8 teaspoons (like 500 mL), it rounds to the nearest tablespoon above 2 cups, the nearest teaspoon above 1/4 cup, or the nearest 1/4 teaspoon below, and says “about”.

Ingredient weights

Weights per cup come from King Arthur Baking’s ingredient weight chart (consulted October 28, 2026). Rows that the chart gives per 1/2 cup or per tablespoon are scaled to 1 cup. Flour assumes it is spooned into the cup and leveled; brown sugar is packed. Butter uses the US stick, which is 4 oz by weight. Water is calculated from its volume (about 0.998 g per mL at room temperature).

A cup of a dry ingredient can vary by 10% or more depending on how it is filled. For baking, weighing is more reliable.

Cans and packages

The ounces printed on cans, jars and yogurt cups are net weight. When a page says how many cups are in such a container, that figure is an estimate based on the food’s density and is always marked “about”.

Corrections

If you find an error, write to hello@howmanyouncesinacup.net. Confirmed errors are fixed in the engine or the source table, which corrects every page that uses the value.