Milliliters to Cups: Water and Liquid Conversions
How ml and liters convert to US cups, UK cups, and fl oz for water and thin liquids, including why US and UK cup sizes differ and how that affects recipe liquid measurements.
Liquid measurement seems like it should be the easy case — water doesn't compress, clump, or pack differently depending on technique — and it mostly is, but the unit itself, 'a cup,' still isn't a single fixed volume worldwide. The US legal cup is 240ml, the US customary cup used in most cooking measurement is 236.6ml (rounded to 240 for practical purposes), the UK/Commonwealth cup is 250ml, and Japan uses a 200ml cup for rice cookers and some recipes. None of these differences matter much for a splash of milk in coffee, but they compound fast in a recipe with multiple cups of liquid — bread dough hydration, soup stock, or a braising liquid — where a 4% (US vs. rounded) to 4.2% (US vs. UK) gap per cup adds up across several cups. This guide gives you the conversion table for water and thin liquids across the systems you're likely to encounter.
US cup = 236.6ml, rounded to 240ml for cooking
The precise US customary cup is 236.588ml, but virtually every US recipe, measuring cup, and cookbook rounds this to 240ml for simplicity — the difference (about 1.4%) is negligible for cooking purposes. When this guide or any US recipe says '1 cup water,' it means 240ml unless a recipe specifically flags scientific/legal precision, which essentially never happens outside of pharmaceutical contexts.
UK/Commonwealth cup = 250ml
The UK, along with Canada (for metric conversions) and much of the Commonwealth, generally defines a metric cup as 250ml, about 4.2% larger than the rounded US cup. This is a small enough gap that a single cup of water in a soup won't ruin anything, but in bread baking, where hydration percentage is calculated precisely against flour weight, using a UK 250ml cup where a US recipe means 240ml adds meaningfully more water than the recipe intended.
💡 Dica: When following a recipe and you're not sure whether it means a US or UK/metric cup, check the recipe's country of origin or unit conventions elsewhere in the ingredient list (oz vs. g, °F vs. °C) as a clue.
Fluid ounces: 1 US cup = 8 fl oz = 240ml
In the US measuring system, 1 cup equals 8 fluid ounces, and 1 fluid ounce equals about 29.6ml — so 8 fl oz × 29.6ml = 236.6ml, consistent with the precise US cup figure. UK fluid ounces are slightly different (28.4ml each), so a UK pint (20 fl oz) is not the same as a US pint (16 fl oz) — this is a common trap when a recipe measures liquid in pints or fl oz rather than cups or ml.
Common conversions: 1/4, 1/3, 1/2, 3/4 cup in ml
Using the rounded US 240ml cup as the base: 1/4 cup = 60ml; 1/3 cup = 80ml; 1/2 cup = 120ml; 2/3 cup = 160ml; 3/4 cup = 180ml; 1 cup = 240ml; 2 cups = 480ml (close to 1 US pint, technically 473ml); 4 cups = 960ml (just under 1 liter, which is 1000ml or about 4.2 US cups).
Liters and larger volumes
1 liter equals 1000ml, which converts to about 4.2 US cups or 4 UK/metric cups (250ml each) — this is why some international recipes round a liter to '4 cups' for simplicity, which slightly undercounts against the true US cup conversion. For large-batch cooking like stock or brine, working directly in liters and milliliters rather than converting to cups avoids the accumulated rounding error of stacking cup fractions.
💡 Dica: For any liquid measurement over 2-3 cups, switch to a liquid measuring cup marked in both ml and cups if you have one — it eliminates the need to do fraction math mid-recipe.
Why liquid measuring cups and dry measuring cups aren't interchangeable
A liquid measuring cup (the clear kind with a spout, meant to be read at eye level with the liquid settling to its own level) and a dry measuring cup (the kind meant to be leveled with a straight edge) hold the same volume, but using a dry cup for liquid risks spilling and inaccurate reading, while using a liquid cup for dry ingredients like flour makes it nearly impossible to level accurately, since there's no flat rim to scrape against. Match the tool to the ingredient type, not just the number on the label.
Perguntas frequentes
How many ml is 1 cup of water?
1 US cup of water is 240ml (precisely 236.6ml, rounded for cooking purposes). A UK or metric cup, used in the UK and much of the Commonwealth, is 250ml instead — about 4.2% larger than the US cup.
Is a UK cup the same as a US cup?
No. A US cup is 240ml (rounded from 236.6ml) while a UK/metric cup is 250ml. The gap is small for a single cup but compounds across a recipe with multiple cups of liquid, particularly in bread baking where hydration percentage is precise.
How many cups is 1 liter?
1 liter (1000ml) is about 4.2 US cups or exactly 4 UK/metric cups (since a metric cup is defined as 250ml). Some recipes round 1 liter to '4 cups' for simplicity, which slightly undercounts against the true US cup conversion.
How many fluid ounces are in a cup?
1 US cup equals 8 US fluid ounces (240ml total, 30ml per fl oz approximately). UK fluid ounces are a different size (28.4ml each), so US and UK fl oz measurements aren't directly interchangeable despite sharing the name.
Should I use a liquid or dry measuring cup for water?
Use a liquid measuring cup — the clear cup with a spout and pour line, read at eye level — for water and other liquids. Dry measuring cups, meant to be leveled with a straight edge, are harder to read accurately for liquids and risk spilling.
For everyday cooking, 1 US cup = 240ml is the number to memorize and it will serve you almost all the time. The moment you're working with a UK, Australian, or otherwise non-US recipe, or a precision application like bread hydration, switch to converting through milliliters directly rather than assuming cups match across systems — the 4% gap between US and UK cups is small per cup but adds up fast across a full recipe.
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