Kitchen Measurement Conversions That Actually Matter
Kitchen measurement conversions with exact NIST factors: cups to ml, ounces to grams, Celsius to Fahrenheit, plus why volume-to-weight depends on the ingredient.
By The UnitFig Editorial Team · September 10, 2026 · reviewed against NIST and SI reference sources
The Core Problem: Volume and Weight Are Not the Same Thing
Most kitchen confusion comes from mixing two different kinds of measurement. Volume measures how much space an ingredient takes up (cups, tablespoons, milliliters). Weight measures how heavy it is (grams, ounces). A cup of flour and a cup of honey fill the same space but weigh very differently, because their densities differ.
That single fact explains almost every "my recipe came out wrong" story. When a recipe gives cups but your scale reads grams, you cannot use a single fixed number unless you also know the ingredient. The tables below separate the conversions that are always exact from the ones that depend on what is in the spoon.
The Exact, Always-True Conversions
These factors are defined by U.S. federal standards (NIST Handbook 44 and the international system) and never change. The U.S. customary cup is exactly 8 fluid ounces, and one fluid ounce is exactly 29.5735 milliliters.
1 US cup = 236.588 ml
1 US fluid ounce = 29.5735 ml
1 tablespoon (tbsp) = 14.7868 ml
1 teaspoon (tsp) = 4.92892 ml
1 ounce (weight) = 28.3495 g
1 pound = 453.592 g
For temperature, the formula is exact: °F = (°C × 9/5) + 32. So 180 °C is 356 °F, 200 °C is 392 °F, and 220 °C is 428 °F. Our Celsius to Fahrenheit converter does it to any decimal you need.
Where Cups-to-Grams Gets Tricky
Common Ingredients, Approximate Weights
Because density varies, a "cup" of each ingredient weighs a different amount. The figures below are the standard spoon-and-level weights used in most U.S. test kitchens. Scooping the cup directly into the bag (the "dip and sweep" method) packs more in and shifts these numbers upward.
All-purpose flour: 1 cup ≈ 120 g
Granulated sugar: 1 cup ≈ 200 g
Packed brown sugar: 1 cup ≈ 220 g
Butter: 1 cup = 2 sticks = 227 g (1 stick = 113 g = ½ cup)
Milk or water: 1 cup ≈ 240 g (close to its 236.6 ml volume because the density is near 1 g/ml)
Cocoa powder: 1 cup ≈ 85 g
These are why a digital kitchen scale is the most reliable upgrade for baking. Weight is repeatable; a "cup" is not.
Why Baking Cares More Than Cooking
In savory cooking, a little more or less flour or liquid is forgiving. In baking, the ratio of flour to liquid to fat determines structure, so small weight errors compound. Professional bakeries work entirely in grams for this reason. If a recipe only gives cups, convert once with a scale and write the gram number in the margin — your next batch will match the first.
A Practical Reference Table
Keep this on the fridge. All volume and weight figures use the exact NIST factors above; the ingredient rows are the spoon-and-level approximations.
1 cup → 236.6 ml → (flour) 120 g / (sugar) 200 g / (water) 240 g
1 tbsp → 14.79 ml → (butter) 14.2 g
1 tsp → 4.93 ml → (salt) ~6 g
1 oz → 28.35 g
1 lb → 453.6 g
180 °C → 356 °F
200 °C → 392 °F
When a recipe says "1 cup" and you only have a scale, pick the ingredient row rather than a generic conversion — that is the difference between a cake that rises and one that does not.
Frequently Asked Questions
Is 1 cup always 236.6 ml?
For U.S. recipes, yes — one customary cup is exactly 236.588 ml by federal standard. Note that a "metric cup" used in Australia and New Zealand is 250 ml, and a Japanese cup is 200 ml, so check which system your recipe assumes before converting.
Why does my cup of flour weigh differently each time?
Because scooping compresses the flour. The standard 120 g figure assumes you spoon flour lightly into the cup and level the top. Dipping the cup into the bag can add 20–30 g. A scale removes the variation entirely.
Can I convert ounces to grams the same way for liquid and dry?
The weight conversion (1 oz = 28.3495 g) is the same, but "ounce" is ambiguous: a fluid ounce is a volume (29.57 ml) while an ounce is a weight. Recipe writers usually mean weight for solids and fluid ounces for liquids — read the context before converting.
Do I really need a kitchen scale?
For reliable baking, yes. A digital scale that reads grams removes the single biggest source of inconsistent results: the unreliable "cup." For casual stovetop cooking, cups are fine.
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Quick Summary
Volume and weight are different measurements, so cups-to-grams only works when you name the ingredient. Use the exact NIST factors for liquids and temperature, and the standard spoon-and-level weights for dry goods — or skip the guesswork with a kitchen scale.
Related Guide
Metric vs Imperial: Why Both Systems Matter and How to Convert Between
Metric (SI) runs most of the world; US customary/imperial is used in the US. Learn where each applies and convert length, weight, and volume with exact factors.
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Disclaimer
Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.
Exact Constants & Authoritative Sources
Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.
- EXACT1 US gallon (gal) = 3.785411784 litres (exact, 231 in³)
- EXACT1 US fluid ounce (fl oz) = 29.5735295625 mL (exact, 1/128 gal)
- EXACT1 US cup = 236.5882365 mL (exact, 8 fl oz)
- EXACT1 US pint (pt) = 473.176473 mL (exact, 16 fl oz)
- EXACT1 US quart (qt) = 946.352946 mL (exact, 32 fl oz)
- EXACT1 litre (L) = 1000 millilitres (definition)
Common Pitfalls & How to Avoid Them
US vs. Imperial (UK) cups
A US cup is 236.59 mL, but a UK/metric cup is 250 mL and an Imperial cup is ~284 mL. Recipes from different countries are not interchangeable drop-in.
Fluid ounce is volume, not mass
A US fl oz is 29.57 mL of volume. 1 fl oz of water ≈ 29.57 g, but 1 fl oz of honey or oil weighs more. Do not treat fluid ounces as grams.
Teaspoon/tablespoon sizes differ
1 US tbsp = 14.7868 mL; 1 US tsp = 4.92892 mL. Metric measuring spoons are 15 mL and 5 mL — close but not exact; for baking precision use weighed grams.
A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.
Authoritative sources for this page
- NIST (U.S. National Institute of Standards and Technology) — NIST SP 330 — The International System of Units (SI), 2019 edition
- BIPM (International Bureau of Weights and Measures) — SI Brochure — The International System of Units (9th edition)
Last Updated 2026 | This article was reviewed for accuracy