Kitchen Measurement Conversions: A Cook's Guide to Metric and US Customary
Recipes from outside the US almost always use metric measurements, grams and milliliters instead of cups and ounces. This guide covers the actual conversion ladder US kitchens run on, how it lines up with metric, and the one issue that trips up more recipe conversions than anything else: the difference between measuring by volume and measuring by weight.
The US Customary Kitchen Ladder
US kitchen measures form a fixed, exact chain: 1 cup equals 8 fluid ounces, equals 16 tablespoons, equals 48 teaspoons. Every step in that chain is an exact defined ratio, not an approximation, because it all derives from the exact US fluid ounce (29.5735295625 mL). See the full breakdown on the Cooking & Baking converter.
| US Unit | Equivalent | In mL |
|---|---|---|
| 1 teaspoon (tsp) | 1/3 tablespoon | 4.9289 mL |
| 1 tablespoon (tbsp) | 3 teaspoons | 14.7868 mL |
| 1 fluid ounce (fl oz) | 2 tablespoons | 29.5735 mL |
| 1 cup | 8 fl oz / 16 tbsp | 236.5882 mL |
Converting Cups, Tablespoons, and Fluid Ounces to Metric
For any liquid or volume-measured ingredient, water, milk, oil, honey by volume, the conversion is a straight multiplication using the table above. Use cups to mL, tablespoons to cups, or fluid ounces to cups directly rather than estimating.
The Weight vs Volume Problem for Dry Ingredients
Here's where most recipe conversions actually go wrong: a cup of flour and a cup of sugar don't weigh the same amount, because volume measures space, not mass, and different dry ingredients pack to different densities. A US recipe measuring flour "by the cup" and a metric recipe measuring it "by the gram" aren't using directly interchangeable numbers, the gram figure depends on how densely that specific ingredient was packed into the cup.
The safest approach, and the one NIST's own household measurement guidance recommends, is to convert dry ingredients by weight whenever a metric recipe gives one: use a kitchen scale and the ingredient's specific gram-per-cup figure rather than assuming a universal cup-to-gram ratio. If a recipe only gives volume for both systems, the Weight & Mass converter and Volume converter handle each half of the problem, but they can't substitute for a real ingredient-specific density figure.
Common Reference Points
| US Measure | Metric (approx.) |
|---|---|
| 1 tsp | 5 mL |
| 1 tbsp | 15 mL |
| 1/4 cup | 59 mL |
| 1 cup | 237 mL |
| 1 quart | 0.95 L |
| 1 gallon | 3.79 L |
These are the US customary values; note that a UK or Australian "cup" and "tablespoon" are sized slightly differently, covered in the US vs UK imperial guide.
Frequently Asked Questions
Is a metric cup the same as a US cup?
No. A US cup is exactly 236.5882365 mL, while a metric cup (used in Australia and a few other countries) is a rounder 250 mL, about 5.6% larger. Check which convention a recipe is using before assuming a direct swap.
Why do professional bakers weigh ingredients instead of using cups?
Weight is a consistent, repeatable measurement regardless of how an ingredient is packed or settled, while a "cup" of flour can vary noticeably depending on whether it's scooped and leveled or sifted first. Weighing removes that variability, which matters most in baking, where ratios affect texture and rise.