Vol. XXIII · The Everyday Cook Plate 4 of 12conversions, units, grams, cups, ounces, pounds, millilitres, tablespoon, teaspoon, Celsius, Fahrenheit, gas mark, 斤, 两, oven temperature, metricT

Units and Conversions.

A US cup of flour is 125 g by the standard, and anywhere from 110 to 150 g in a real kitchen. A gram is a gram.

Recipes travel between measuring systems. Weight is the most reliable: grams and kilograms; ounces (28.35 g) and pounds (454 g); and in China the market units 斤 (500 g) and 两 (50 g), still used for buying meat and vegetables. Volume is fine for liquids — millilitres; the US cup (237 mL), the metric cup (250 mL); the tablespoon (15 mL, but 20 mL in Australia) and teaspoon (5 mL) — but unreliable for powders, because how a cup is filled changes its weight by a fifth or more (I.5). Converting a cup of a dry ingredient to grams needs a density, which differs for each ingredient.

Temperatures convert exactly: °F = °C × 9/5 + 32. Gas marks, on British gas ovens, step by 25 °F (about 14 °C) from mark 1 at 275 °F (140 °C). Fan ovens run hotter than conventional ones at the same setting, so recipes for conventional ovens are reduced by about 20 °C for fan (II.7). The workshop converts.

Below: grams in the number of US cups you choose of the ingredient you choose (standard cup weights), and an oven temperature in °F converted to °C and gas mark (exact formula; gas marks rounded), with a table of other units.

What you will learn
Workshop
Cup weights: standard values for a spooned-and-levelled US cup (CK.D.engine.cup, from USDA and industry tables); real cups vary by about a fifth. °C = (°F − 32) × 5/9, exact. Gas mark = (°F − 250) ÷ 25, rounded (mark 1 = 275 °F); below mark 1 the marks are ¼ and ½.

Convert once, write the grams

A standard cup of plain flour is about 125 g, of sugar 200 g and of honey 339 g: the same cup holds nearly three times the weight of honey as of flour, which is why cups cannot be converted with a single number. 180 °C is 356 °F (often written 350 °F, gas mark 4); 350 °F in a fan oven is about 160 °C. When you use a recipe in cups or ounces, convert it once to grams and °C, write the numbers on the page, and cook from them ever after.

Practical habits: a digital scale that reads to 1 g (and a small one to 0.1 g for yeast, salt and spices) makes conversions unnecessary; set the scale to zero with the bowl on it and weigh each ingredient in turn. For liquids, 1 mL of water weighs 1 g; milk and stock are close enough. Check your oven with a thermometer (II.7), because a dial's 180 °C may be 165 or 200. When a Chinese recipe says 半斤 of pork, that is 250 g; 二两 of noodles, 100 g.

At the stove

Spoon flour into a cup and level it, weigh it; then scoop the cup straight from the bag, level it, and weigh again. Note the difference.

The metric system was introduced in France in 1795; the gram was defined as the mass of a cubic centimetre of water at its melting point. China fixed the 市斤 at exactly 500 g in 1959, which is why 斤 and 两 convert so neatly today.

Terms

斤 and 两
Chinese market units: 500 g and 50 g.
Gas mark
British gas oven setting; mark 4 is about 180 °C.
US cup
237 mL; for dry ingredients its weight varies.
Fan oven
An oven with a fan; set about 20 °C lower.
Weigh, don't scoop: a cup's weight depends on the ingredient and the filling. Temperatures convert exactly (°F = °C × 9/5 + 32); gas mark 4 ≈ 180 °C; 1 斤 = 500 g, 1 两 = 50 g. Set fan ovens 20 °C lower.

Sources

  1. A teaching value chosen for the course: the right order of magnitude and shape, not a measurement of a particular food.