Anyone who’s ever followed a recipe from a different country has run into the same puzzle: a cup isn’t always a cup. That 1/3 cup measurement on your screen might mean 78.8 ml or 80 ml — and the difference, though small, can throw off a delicate cake batter.

4 related posts

US cup 1/3: 78.8 ml ·
Metric cup 1/3: 80 ml ·
Tablespoons in 1/3 cup: 5 tbsp + 1 tsp

Quick snapshot

1Confirmed facts
2What’s unclear
3Timeline signal
  • No timeline data applicable for this measurement topic
4What’s next
  • Check your recipe’s origin: US, UK, Canada, or Australia — each uses a different base cup
  • Use a kitchen scale for the highest precision, especially for flour and sugar

Six key conversion facts, one pattern: the cup system you start with determines the right milliliter value.

Measurement Value Source
1/3 cup (US) = 78.8 ml 78.8 ml Weekend Bakery, baking resource
1/3 cup (metric) = 80 ml 80 ml Anna Olson, professional pastry chef
1/3 cup in tablespoons 5 tbsp + 1 tsp Just One Cookbook, recipe resource
1/3 cup in teaspoons 16 tsp Weekend Bakery, baking resource
1/3 cup water weight (metric) 80 g Cotswold Flour, UK flour mill
1/3 cup all-purpose flour weight ≈ 43 g Anna Olson, professional pastry chef

How much is 1/3 cup in ml?

US cup to ml

  • The US customary cup is defined as 236.6 ml (exact: 236.5882365 ml). One third of that is 78.8 ml (Weekend Bakery, baking resource).
  • Most US-centric conversion charts round this to 79 ml for simplicity.

Metric cup to ml

  • The metric cup, used in the UK, Canada, Australia, and New Zealand, is exactly 250 ml. One third equals 80 ml (Anna Olson, professional pastry chef).
  • That 1.2 ml difference per third cup adds up across larger batches.

Why the difference?

  • The US customary system is based on the imperial pint (473.2 ml), while the metric cup is a clean decimal of the litre.
  • A UK cup aligns with the metric system at 250 ml, but older British recipes used a 284 ml cup based on the imperial pint (Cotswold Flour, UK flour mill).

Bottom line: A 1/3 cup measurement is not universal. US-based bakers get 79 ml; UK/Commonwealth bakers get 80 ml. For recipes that blend systems, use the 80 ml standard unless the recipe specifically calls out US customary.

The trade-off

Using 80 ml when the recipe expects 79 ml adds roughly 1% extra liquid per third cup. In a loaf cake with two cups of liquid, that’s a 6 ml surplus — negligible for savoury dishes, noticeable for delicate puff pastry or macarons.

Is 80ml a 1/3 cup?

When 80 ml is accurate

  • In any metric-based cup system (Canada, Australia, New Zealand), 1/3 cup is exactly 80 ml (Anna Olson, professional pastry chef).
  • Many international recipe sites, including Weekend Bakery, standardise on 80 ml for all non-US recipes.

80 ml vs 79 ml – negligible difference

  • The difference between 79 ml and 80 ml is 1.26%, which falls within the margin of error for most home measuring cups (Cook Like Czechs, US-Metric converter).
  • For baking, where ratios matter more than absolute precision, this variance is generally safe.

Why 80 ml is commonly used

  • 80 ml is the cleanest rounded figure for 1/3 of 250 ml — no decimals, no fractions.
  • It appears as the standard conversion in nearly every major baking guide, from Anna Olson to Cotswold Flour.

The implication: If the recipe came from a US cookbook or website, use 79 ml (78.8 ml exact). For any other English-language source, 80 ml is almost certainly what the author intended.

How do I measure 1/3 cup?

Using a measuring cup

  • Fill a standard 1/3 cup dry measuring cup to the brim and level it with a straight edge.
  • For liquids, use a transparent cup with ml markings — fill to the 80 ml line for metric recipes, or 79 ml for US.

Using tablespoons

  • 1/3 cup equals 5 tablespoons plus 1 teaspoon (WikiHow, practical cooking guides).
  • Each tablespoon is 15 ml; the extra teaspoon adds 5 ml — total 80 ml.
  • For US recipes: use 5 tbsp + 1 tsp, which yields 79 ml (5 × 15 + 5 = 80 ml, but the rounding is acceptable).

Using a kitchen scale

  • Weighing is the most accurate method, especially for dry ingredients.
  • Water and milk: 80 g (metric) or 79 g (US) per 1/3 cup (Cotswold Flour, UK flour mill).
  • All-purpose flour: ~43 g per 1/3 cup (Anna Olson, professional pastry chef).
  • Granulated sugar: ~67 g per 1/3 cup.
  • Olive oil: ~72 g per 1/3 cup.
Why this matters

For ingredients like flour, scooping vs. spooning changes weight by up to 20%. A kitchen scale eliminates that guesswork entirely. If you bake more than once a week, a scale pays for itself in consistent results.

Is 1/3 or 1/4 a cup more?

Volume difference in ml

  • 1/3 cup is 1.33 times larger than 1/4 cup.
  • In US terms: 1/3 cup = 79 ml, 1/4 cup = 59 ml — a 20 ml difference (Just One Cookbook, recipe resource).
  • In metric terms: 1/3 cup = 80 ml, 1/4 cup = 60 ml — also 20 ml (Weekend Bakery, baking resource).

Visual comparison

  • A 1/3 cup measure is noticeably fuller than a 1/4 cup — roughly the height of two stacked dice.
  • If you pour 1/3 cup into a 1/4 cup, the 1/4 cup fills and overflows.

When it matters

  • In baking, that 20 ml difference between 1/4 and 1/3 cup can alter the hydration ratio of a dough enough to change texture.
  • For daily cooking (sauces, rice, dressings), the 20 ml variance is far less critical.

How many ml is 1/2 cup?

1/2 cup in US and metric

  • 1/2 US cup = 118 ml (rounded to 120 ml in many charts) (Weekend Bakery, baking resource).
  • 1/2 metric cup = 125 ml (Anna Olson, professional pastry chef).

1/4 cup, 2/3 cup, 1 cup conversions

  • 1/4 cup (US) = 59 ml, (metric) = 60 ml
  • 2/3 cup (US) = 158 ml, (metric) = 160 ml (Just One Cookbook, recipe resource)
  • 1 cup (US) = 236.6 ml, (metric) = 250 ml

The pattern: For every fractional cup, the metric system gives you clean multiples of 10, while the US system yields decimals. The larger the fraction, the wider the gap becomes — at 2 cups, the US vs metric difference hits 26.8 ml, more than a full tablespoon.

The catch

UK cooks face a third system: the imperial cup of 284 ml. A 1/3 imperial cup equals 94.7 ml — a full 14.7 ml more than the metric version. Always check whether your British recipe predates or postdates the 1970s metrication shift.

Related reading: **Greek Pasta Salad Recipe** · **Ninja Deluxe Kitchen System Review and Comparisons**

If you’re converting other fractional cup measurements, the quarter cup to ml conversion offers exact US and metric equivalents for a quarter cup.

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Frequently asked questions

What is 1/3 cup in milliliters for water?

For water, 1/3 cup is 78.8 ml (US customary) or 80 ml (metric). Weight is equivalent: 79 g (US) or 80 g (metric) (Cotswold Flour, UK flour mill).

Is 1/3 cup the same in the UK?

In modern UK baking, 1/3 cup = 80 ml (metric cup). Older UK recipes used an imperial cup of 284 ml, making 1/3 equal 94.7 ml. Always check the recipe’s publication date (Cotswold Flour, UK flour mill).

How many ounces is 1/3 cup?

1/3 US cup = 2.67 fluid ounces; 1/3 metric cup = 2.7 fluid ounces. By weight, 1/3 cup of water weighs 2.8 oz (US) or 2.9 oz (metric).

Can I use a 1/4 cup and a 1/8 cup to make 1/3 cup?

No. 1/4 cup + 1/8 cup = 3/8 cup, which is 1/24 cup more than 1/3 cup. The difference is about 10 ml — enough to alter a baking recipe.

Why do some websites say 1/3 cup is 75 ml?

Some conversion tables, including Just One Cookbook, recipe resource, list 75 ml for 1/3 cup. This appears to be an older rounding standard no longer used by major baking authorities. Most modern sources use 80 ml.

How do I convert 1/3 cup to ml for ingredients other than water?

Volume conversion (ml) stays the same regardless of ingredient. The weight (grams) changes: 1/3 cup flour ≈ 43 g, sugar ≈ 67 g, oil ≈ 72 g (Anna Olson, professional pastry chef).

Is 1/3 cup equal to 5 tablespoons?

Not exactly. 5 tablespoons = 75 ml using the 15 ml per tablespoon standard. 1/3 cup = 80 ml (metric) or 79 ml (US), so you need 5 tablespoons plus 1 teaspoon (WikiHow, practical cooking guides).

What is the difference between a US cup and a metric cup?

A US cup is 236.6 ml, based on the imperial pint. A metric cup is 250 ml, based on the litre. The 13.4 ml gap means that over a full cup, the metric recipe uses about 5.7% more liquid (Cook Like Czechs, US-Metric converter).

Whether you’re baking a birthday cake or scaling a family pasta salad recipe, the 1/3 cup measurement is one of the most common pitfalls in cross-border cooking. For the home cook in North America using US recipes, the safe play is 79 ml per third cup. For everyone else working with metric or Commonwealth recipes, 80 ml is the reliable standard — and a kitchen scale is the only way to guarantee precision across every ingredient.