Key takeaways
- NIST's approximate kitchen equivalents: 1 teaspoon is 5 mL, 1 tablespoon 15 mL, 1 fluid ounce 30 mL and 1 cup 240 mL.
- US nutrition labels use the same rounded figures by rule: a cup means 240 mL and an ounce by weight 28 g.
- A cup is a volume, so its weight depends on the ingredient: USDA data put a cup of all-purpose flour at 125 g, granulated sugar at 200 g and honey at 339 g.
- NIST calls weighing ingredients on a kitchen scale a best practice for accuracy, and warns that using a dry measuring cup for liquids is a common source of error.
- A 'moderate' oven in older recipes is 180–190°C, or 350–375°F, according to NIST's guide.
Recipes travel between countries and decades, and their units do not always come along cleanly. This guide gathers the conversions you need most, using the National Institute of Standards and Technology's Metric Kitchen guides, the FDA's labelling definitions and USDA food data, and explains the conversion that no single factor can handle: cups to grams.
Volume: spoons, cups and millilitres
NIST's Metric Kitchen publishes the approximate equivalents in the middle column for home cooking. The right-hand column gives the exact US value, worked out from the conversion factors in NIST's Guide to the SI (1 teaspoon = 4.928922 mL, 1 tablespoon = 14.78676 mL, 1 fluid ounce = 29.57353 mL, 1 cup = 236.5882 mL, 1 gallon = 3.785412 L):
| US customary | NIST kitchen approximation | Exact US value |
|---|---|---|
| ¼ teaspoon | 1.25 mL | 1.23 mL |
| ½ teaspoon | 2.5 mL | 2.46 mL |
| 1 teaspoon | 5 mL | 4.93 mL |
| 1 tablespoon (½ fluid ounce) | 15 mL | 14.79 mL |
| 1 fluid ounce | 30 mL | 29.57 mL |
| ¼ cup | 60 mL | 59.1 mL |
| ⅓ cup | 80 mL | 78.9 mL |
| ½ cup | 120 mL | 118.3 mL |
| ¾ cup (6 fluid ounces) | 180 mL | 177.4 mL |
| 1 cup | 240 mL | 236.6 mL |
| 2 cups (1 pint, 16 fluid ounces) | 480 mL | 473.2 mL |
| 4 cups (1 quart, 32 fluid ounces) | 950 mL | 946.4 mL |
| 1 gallon (4 quarts, 16 cups) | 3.84 L | 3.785 L |
The rounding is harmless for a spoonful, but it grows with volume: NIST's gallon figure is about 55 mL more than a true US gallon.
Food labels use the same round numbers by rule. Under the FDA's nutrition labelling regulation, a teaspoon means 5 mL, a tablespoon 15 mL, a cup 240 mL, a fluid ounce 30 mL and an ounce by weight 28 g. NIST also notes that some older recipes use metric "cup and spoon" measures, which are slightly larger than US ones and can often be used interchangeably.
Weight: ounces, pounds and grams
| US customary | NIST kitchen approximation | Exact value |
|---|---|---|
| 1 ounce (by weight) | 28 g | 28.35 g |
| ¼ pound (4 ounces) | 114 g | 113.4 g |
| 1 pound (16 ounces) | 454 g | 453.6 g |
| 2.2 pounds | 1 kg | 0.998 kg (1 kg is 2.205 pounds) |
The exact figures use NIST's factors of 28.34952 g per avoirdupois ounce and 0.4535924 kg per pound. NIST's tips also point out that the US fluid ounce, a unit of volume, and the avoirdupois ounce, a unit of weight, are different units, so a recipe's "ounces" need checking before you convert them.
Why a cup of flour is not a cup of sugar
A cup is a volume, so what it weighs depends on what is in it. USDA's SR Legacy data list these cup weights:
| Ingredient | 1 cup weighs |
|---|---|
| All-purpose white flour | 125 g |
| Brown sugar, unpacked | 145 g |
| White rice, raw | 185 g |
| Granulated sugar | 200 g |
| Olive oil | 216 g |
| Brown sugar, packed | 220 g |
| Butter | 227 g |
| Table salt | 292 g |
| Honey | 339 g |
A worked example. A recipe calls for 2 cups of flour and 1 cup of sugar. Using one "cup equals 240 mL" conversion tells you nothing about grams. Using the table: 2 × 125 g = 250 g of flour and 200 g of sugar. Notice too that brown sugar weighs 145 g a cup loose but 220 g packed, a 52% difference from how firmly you fill the cup. That is why weights make recipes repeatable.
How NIST says to measure
NIST's culinary measurement tips are practical:
- Weigh when you can. Measuring by mass on a kitchen scale is the best practice for accuracy.
- Use the right cup. Dry measuring cups are for dry ingredients and fluid cups for liquids; swapping them is a common source of error.
- Read liquids at eye level, with the cup on a level surface.
- Level off dry ingredients with a straight edge.
- Convert traditional recipes by weighing: measure an ingredient with the original tool, then weigh it and record the grams.
Oven temperatures
Heirloom and vintage recipes may describe ovens rather than give numbers. NIST translates those legacy terms into approximate equivalents:
| Description | °C | °F |
|---|---|---|
| Slow | 150–160 | 300–325 |
| Moderately slow | 160–180 | 325–350 |
| Moderate | 180–190 | 350–375 |
| Moderately hot | 190–200 | 375–400 |
| Hot | 200–230 | 400–450 |
| Very hot | 230–260 | 450–500 |
To convert any temperature, °C = (°F − 32) × 5/9. NIST's oven figures are rounded: by the formula, 350°F is about 177°C and 375°F about 191°C. For food safety, NIST's temperature page lists minimum internal temperatures measured with a food thermometer, which is a different measurement from oven temperature; safe cooking temperatures gives those.
Scaling and conversions together
Conversions compound when you scale a recipe. Recipe scaling and serving sizes covers what does and does not multiply cleanly. Easy Recipes & Meal Planner, one of our health and nutrition apps, starts each recipe at one serving and scales ingredient amounts, and nutrition where it is available, to the servings you choose.
Good to know
Frequently asked questions
How many millilitres are in a cup?
How many grams are in a cup of flour?
What oven temperature is a moderate oven?
Why weigh ingredients instead of using cups?
Sources
- Metric Kitchen: Cooking Measurement Equivalencies (opens in a new tab)National Institute of Standards and Technology — accessed
- Metric Kitchen: Culinary Measurement Tips (opens in a new tab)National Institute of Standards and Technology — accessed
- Metric Kitchen: Culinary Temperature (opens in a new tab)National Institute of Standards and Technology — accessed
- NIST Guide to the SI, Appendix B.9: Factors for units listed by kind of quantity or field of science (opens in a new tab)National Institute of Standards and Technology — accessed
- 21 CFR 101.9: Nutrition labeling of food (opens in a new tab)eCFR, US Government Publishing Office — accessed
- FoodData Central: SR Legacy (April 2018 release) (opens in a new tab)US Department of Agriculture, Agricultural Research Service — accessed
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