How Many ml in a Cup? US, Metric, UK Conversions Compared

If you’ve ever followed a recipe from a British cookbook and found your cake turned out denser than expected, you’ve run into the age-old “cup” problem: the US customary cup holds 236.588 ml, while the metric cup is 250 ml — a 13.4 ml difference that adds up fast. This guide walks through every major cup standard so your next international recipe actually works.

US customary cup: 236.588 ml · US legal cup (nutrition): 240 ml · Metric cup (most countries): 250 ml · Imperial cup (UK, retired): 284.131 ml · Canadian cup (historical): 227.3045 ml

The four major cup standards differ in volume, as shown in the table below.

Is 250 ml equal to 1 cup?

US customary cup vs metric cup

Answer: it depends on which cup standard your recipe uses. The US customary cup is exactly 236.588 ml (Wikipedia: Cup (unit)), while the metric cup is 250 ml. These two differ by about 13.4 ml — roughly one tablespoon. So 250 ml is equal to 1 metric cup, but it is about 1.06 US customary cups.

When 250 ml is a full cup

Many modern recipes from outside the US treat 250 ml as exactly one cup. Australia, New Zealand, South Africa, and Ireland all follow the metric cup standard (Adagio Blog: Cooking Measurements Guide). The US legal cup, used on nutrition labels, is also defined as 240 ml under federal labeling law, so 250 ml is slightly more than a legal cup.

The pattern: knowing the recipe’s origin is the first step to accurate conversion.

What is 1 cup in ml in the UK?

Imperial cup vs metric cup in modern UK

The historical imperial cup equals 284.131 ml (10 imperial fluid ounces). However, this unit is largely obsolete. Modern UK recipes typically use the metric cup of 250 ml or, increasingly, weights in grams (Wikipedia: Cup (unit)). The delicious. magazine (UK food publication) explicitly publishes US-to-UK cups-to-grams conversion charts, acknowledging that cup measurements in the UK require country-specific interpretation.

Why UK recipes now often use 250 ml

Since the UK adopted the metric system, most contemporary cookbooks have shifted to either metric cups (250 ml) or direct gram measurements. The imperial cup (284.131 ml) survives only in very old recipes or specialised references.

The implication: always check the publication date of a UK recipe before assuming the cup size.

Is 1 cup 200 or 250ml?

Common cup sizes worldwide

1 cup is not 200 ml. The most frequently encountered values are 236.588 ml (US customary), 240 ml (US legal), and 250 ml (metric). Some older Japanese recipes historically used a 200 ml cup, but that standard has been largely replaced by metric measures (Adagio Blog: Cooking Measurements Guide).

Which cup size do most recipes use

• US mainstream recipes: 236.588 ml (customary) or 240 ml (legal).
• Australian, NZ, Irish, South African recipes: 250 ml (metric).
• UK modern recipes: 250 ml (metric) when they use cups at all.
• Canadian recipes: now also 250 ml metric, though a historical Canadian cup was 227.3045 ml (Wikipedia: Cup (unit)).

How many ml are in a cup in Ireland?

Ireland follows the metric cup standard of 250 ml, consistent with other countries like Australia and New Zealand. Modern Irish recipes use 250 ml as one cup, though some older cookbooks may have used imperial or US measures.

The catch: even within a region, cup definitions can vary over time.

How many ml in a cup of water, milk, or oil?

Does the ingredient change the volume?

Volume is volume. A cup of water, milk, or oil all occupy the same number of milliliters — 236.588 (US customary), 240 (US legal), or 250 (metric) — because the cup is a volume measure. The density of the ingredient affects its weight, not its volume (WebstaurantStore: Cooking Measurement Conversion Chart). So 1 US customary cup of milk is also 236.588 ml, just as 1 cup of oil is.

Converting liquid vs dry cups

Liquid and dry measuring cups differ in shape for practical pouring, but they measure the same volume. A “dry cup” and a “liquid cup” both hold the same number of milliliters — the difference is only in the design to allow leveling for dry ingredients and spill-free pouring for liquids.

How many ml is 1/4 cup, 1/2 cup, and 3/4 cup?

Fractional cup conversions to ml

The exact ml values depend on which cup standard you follow. Below is a quick reference for the three most common systems:

Three cup size systems, one conversion pattern: the fractions stay proportional, but the base changes.

The implication: if you’re using a US recipe and a metric measuring cup, every fraction is off by about 2-6%. Over a full recipe, that error compounds — a half cup of sugar becomes 125 ml instead of 118.3 ml, adding roughly 1 tablespoon extra.

Steps for accurate cup-to-ml conversion

1. Identify the recipe’s origin. Check the cookbook’s introduction, the website’s “about” page, or the ingredient list’s unit system. US recipes use fluid ounces; UK/AU recipes often list ml alongside cups.
2. Choose the correct standard. Use US customary (236.588 ml) for US home recipes, US legal (240 ml) for US nutrition labels, and metric (250 ml) for most other countries.
3. Use a conversion table. Keep a printout of the table above in your kitchen. For fractional cups, multiply the fraction by the base ml value: e.g., 1/2 US customary cup = 0.5 × 236.588 = 118.294 ml.
4. Weigh dry ingredients when possible. Even with the right cup volume, flour compaction can vary by 20%. A kitchen scale removes the cup-to-ml guesswork entirely.

What this means for bakers: the safest approach is to learn the cup standard of your recipe source and adjust your measuring tools accordingly. If you own a set of US measuring cups, you don’t need to recalculate — just trust the cups. If you use a metric liquid measure, apply the conversion from the table above.

What’s confirmed vs what’s unclear

“Legal U.S. cup: the measurement used in cooking units, serving sizes, and nutrition labeling in the U.S. One legal cup equals 8 U.S. fluid ounces.”

Masterclass (online culinary education platform)

“1 cup or 8 fluid ounces = 237 ml”

Exploratorium (science museum and educational organisation)

“1 cup is 8 fl oz, which is equivalent to 236.588 ml.”

Reddit r/AskCulinary (community cooking forum)

For home bakers navigating international recipes, the choice between cup standards comes down to a single question: whose cup does your recipe mean? If you guess US customary for an Australian recipe, you’ll under-pour each cup by 13.4 ml. Over four cups of flour, that’s a full tablespoon short — enough to turn a moist scone into a dry puck. The practical fix: check the recipe’s origin, use the conversion table above, and when in doubt, weigh your ingredients in grams.

For cooks navigating different recipe systems, comparing these values with a comprehensive how many mL in a cup guide helps avoid measurement errors when switching between US and metric standards.

Frequently asked questions

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