Cooking Converter: Cups to Grams, Tablespoons to ml and Oven Gas Marks

Volume to volume is exact. The US units all come from the US gallon (231 cubic inches, which is 3,785.411784 ml): a fluid ounce is 29.5735295625 ml, a tablespoon is 14.78676478125 ml, a teaspoon is 4.92892159375 ml and a cup is 236.5882365 ml, which is 16 tablespoons or 48 teaspoons. Other cups and spoons are rounder: the metric teaspoon is 5 ml, the metric tablespoon is 15 ml and the metric cup is 250 ml. On US food labels the rule sets a teaspoon at 5 ml, a tablespoon at 15 ml and a cup at 240 ml (21 CFR 101.9). Australian recipes conventionally use a 20 ml tablespoon. Check which cup and spoon your recipe means and pick it from the list.

Weight from volume uses a density: grams per US cup from a published table. Two sources are offered. USDA FoodData Central (SR Legacy) lists household measures for each food record, for example 1 cup of all-purpose flour is 125 g (food 168894). King Arthur Baking's ingredient weight chart gives 120 g for the same cup. The table below lists both for every ingredient, with the USDA record. When a source gives the weight of part of a cup (113 g for 8 tablespoons of butter, 21 g for a tablespoon of honey), the tool scales it to a full cup. Other cups are scaled by volume from the US cup, so a 250 ml metric cup of flour is 132 g by USDA, not 125 g. Where King Arthur has no matching row (red lentils) the tool uses USDA and says so.

These weights are approximate, and the sources show why. How you fill the cup matters: USDA lists 145 g for a cup of loosely filled brown sugar against 220 g packed, and 100 g for a cup of sifted icing sugar against 120 g unsifted. The two sources differ by up to about 10% on the same ingredient (rolled oats 81 g and 89 g, vegetable oil 218 g and 198 g). King Arthur lists water at 227 g a cup, which is 8 ounces of weight, while a US cup of water by volume is 236.6 ml and weighs about 237 g (USDA). For baking, a kitchen scale is more reliable than any cup.

Oven temperatures use the gas mark scale: gas mark 1 is 275 °F, and each mark adds 25 °F up to gas mark 9 at 475 °F. So gas mark 4 is 350 °F, which is 176.7 °C to one decimal place, and gas mark 6 is 400 °F or 204.4 °C. Printed charts round the Celsius figure to a multiple of 10 and do not follow one rule: Which? prints 180 °C for gas mark 4 and 240 °C for gas mark 9 (exactly 246.1 °C), and the charts do not all agree (gas mark 3 is 160 °C on Which? and 170 °C on Wikipedia). The tool shows the exact conversion and the Which? figure side by side. A fan oven usually runs about 20 °C cooler than a conventional one.

In Sri Lankan kitchens rice and flour are often measured in cups, but the cup is not standard. A rice cooker cup is 180 ml: that is the standard Japanese rice cup, called a go, and Zojirushi says its cookers' water lines are marked for that cup and not for a 240 ml US cup. Other makes may differ, so use the cup that came with your cooker. A tea cup, a mug or a coconut shell measure varies a lot. Fill yours with water, pour it into a measuring jug and type its size into the 'your own cup' box. By the density tables, 180 ml of raw white long-grain rice weighs about 141 g (USDA) or 151 g (King Arthur).