US vs Australian Tablespoon: 15 mL vs 20 mL Explained

An Australian tablespoon holds 20 ml. A US tablespoon holds about 14.79 ml, a figure that recipes and food labels round to 15 ml. That 5 ml gap is not trivial: the Australian tablespoon is roughly a third larger than the tablespoon used almost everywhere else, including the US, the UK, and continental Europe. Measure an Australian recipe with a US or metric tablespoon and you under-fill it by 25%. Do the reverse and you over-fill it by 33%.

The Three Tablespoon Standards, Compared

Three spoon sizes share the name “tablespoon,” and only one of them breaks from the international metric pattern:

The teaspoon barely changes between systems: the US teaspoon is 4.93 ml and the metric teaspoon used in Australia, the UK, and the rest of Europe is 5 ml, a gap too small to matter in a kitchen. The tablespoon is where the real split happens. The Australian tablespoon holds about 35% more than the precise US tablespoon (20 ÷ 14.79 = 1.35) and 33% more than the 15 ml tablespoon used almost everywhere else (20 ÷ 15 = 1.33). Cup sizes split the same way, by the way: 236.588 ml in the US and 250 ml in Australia, which is a separate issue from the spoon gap and worth keeping in mind if the same recipe mixes cups and tablespoons; see cup sizes around the world for that comparison in full, including the Japanese and historic Imperial cup.

Why the US Tablespoon Is Actually 14.79 ml, Not 15

A US tablespoon is defined as 1/16 of a US customary cup. This site’s own converter is built on that relationship: a US cup of 236.588 ml split into 16 tablespoons is 236.588 ÷ 16 = 14.79 ml. That matches the tablespoon’s customary legal definition, maintained by the National Institute of Standards and Technology in NIST Handbook 44, the publication that sets exact US weights and measures.

In everyday cooking almost nobody measures 14.79 ml. US recipe writers, cookbook publishers, and the FDA all round it up to a flat 15 ml. The FDA’s own guidance on metric equivalents of household measures states plainly that “1 tablespoon means 15 mL” for nutrition labeling purposes. Most US measuring spoons sold in stores are stamped with both “1 Tbsp” and “15 mL” on the same spoon, treating the two as interchangeable.

That rounding is harmless by itself: 14.79 ml and 15 ml differ by under 1.5%, well inside the margin of error of a hand-poured spoonful. The rounding only becomes a real problem once a second, genuinely different standard enters the picture, which is exactly what happens with an Australian recipe.

Why Australia’s Tablespoon Is 20 ml

Australia’s tablespoon was set at 20 ml, not 15 ml, during the country’s metrication in the 1970s. According to Wikipedia’s entry on the tablespoon, the 20 ml definition was promulgated by the Metric Conversion Board as Australia converted its cooking measures to the metric system, and it remains the standard specified today in Standards Australia’s AS 1325 for domestic measuring cups and spoons. Every other country that metricated its spoons, including the UK, Canada, and the rest of Europe, settled on 15 ml. Australia is the only one that did not.

The teaspoon did not change. An Australian teaspoon is 5 ml, the same 5 ml used everywhere else in the metric world. Only the tablespoon grew, and it grew to a size that divides evenly by that unchanged teaspoon:

• 1 Australian tablespoon = 4 × 5 ml teaspoons = 20 ml
• 1 metric tablespoon (UK, EU) = 3 × 5 ml teaspoons = 15 ml
• 1 US tablespoon = 3 × 4.93 ml teaspoons = 14.79 ml

If you learned “1 tablespoon equals 3 teaspoons” as a fixed rule, which is true almost everywhere outside Australia, applying it to an Australian recipe under-measures the ingredient by exactly one teaspoon, 5 ml, every single time.

How to Tell an Australian Recipe by the Tablespoon

Nothing on the page announces which tablespoon a recipe means, so the clues are in the surrounding details:

• The author or publication is Australian. Australian food sites, magazines, and cookbooks (a .com.au domain, or a publisher based in Sydney or Melbourne) default to the 20 ml tablespoon unless the recipe states otherwise.
• The spelling gives it away. “Bicarb soda” for baking soda, “caster sugar,” “icing sugar,” “capsicum” for bell pepper, and British-style spellings such as “colour” and “caramelise” are common markers of Australian writing, though British recipes still use the 15 ml tablespoon, not 20 ml.
• The recipe says so directly. Careful Australian writers who expect an international audience often add a note such as “tablespoon = 20 mL” or “Australian tablespoons used” near the ingredient list.
• The tablespoon-to-teaspoon math looks like 1:4. If a recipe’s measurement notes equate 1 tablespoon with 4 teaspoons instead of 3, that is a direct signal of the Australian standard.

When none of these signals are present and the source is ambiguous, treat the tablespoon as 15 ml. That covers the US, UK, Canada, and most of Europe, by far the larger share of English-language recipes online.

What Happens When You Grab the Wrong Tablespoon

The error runs in two directions, and it is not symmetrical.

Using a 15 ml tablespoon on an Australian recipe. An Australian recipe calling for 1 tablespoon of baking powder means 20 ml. Scoop it with a standard 15 ml tablespoon instead, and you get 15 ml, which is 20 minus 15 = 5 ml short. 5 ÷ 20 = 0.25, a 25% under-measure. The cake gets three-quarters of the leavening the recipe was balanced for.

Using a 20 ml Australian tablespoon on a US or metric recipe. A US recipe calling for 1 tablespoon of baking soda means 15 ml (14.79 ml precisely, close enough for a hand measurement). Scoop it with an Australian tablespoon instead, and you get 20 ml, which is 20 minus 15 = 5 ml too much. 5 ÷ 15 = 0.333, a 33% over-measure, a third more leavening than the recipe called for. That is enough to push a cake toward a bitter, metallic aftertaste and an uneven rise.

The same 5 ml gap produces a smaller percentage error going one way (25%) and a larger one going the other (33%), because each percentage is measured against a different starting amount.

The Ingredients Where a Few Milliliters Matters Most

Every tablespoon-measured ingredient is affected by the same percentage error, but the mistake is far more noticeable in some ingredients than others.

Leaveners: baking powder and baking soda. These are used in small volumes precisely because a little goes a long way. A 25% shortfall in baking powder can leave a cake flat and dense; a 33% excess in baking soda can leave a metallic, soapy taste behind. There is very little tolerance on either side.

Cocoa powder. Cocoa affects both flavor and the dry-to-wet balance of a batter. Being a third too heavy or a quarter too light changes the chocolate flavor and how the batter sets.

Oil. A tablespoon or two of oil is often the entire fat content in a quick bread or muffin recipe. An error of 25 to 33% on that one ingredient shows up directly in moisture and tenderness.

Honey and golden syrup. These are dense, sticky liquids where a volume error carries real weight. Honey weighs about 1.44 g per ml (340 g per US cup, and 340 ÷ 236.588 = 1.44). One Australian tablespoon of honey (20 ml) weighs about 20 × 1.44 = 28.8 g. Measure the same “1 tablespoon” with a 15 ml spoon and you get 15 × 1.44 = 21.6 g, a 7.2 g shortfall, again 25%. Golden syrup, being close to honey in density, behaves almost the same way.

How the Mistake Compounds Across a Full Recipe

A single tablespoon error is a fixed percentage, but most recipes use tablespoons for more than one ingredient, and that is where the mistake adds up.

Take a simple Australian chocolate cake step that calls for 3 tablespoons of cocoa powder, 2 tablespoons of oil, and 1 tablespoon of golden syrup. Measured correctly, that is 6 tablespoons × 20 ml = 120 ml combined. Measured with a 15 ml tablespoon instead, it becomes 6 × 15 = 90 ml, a shortfall of 30 ml, still 25% overall.

The percentage itself does not get worse as more ingredients are added. What gets worse is the number of things going wrong at the same time. The cocoa (flavor and dry ratio), the oil (fat and moisture), and the golden syrup (sweetness and browning) are all short by a quarter simultaneously. One ingredient being 25% off is often forgivable. Three functionally different ingredients all being 25% off in the same direction, at the same time, is what actually changes how a finished bake tastes, rises, and browns.

Converting Between Australian, US, and Metric Tablespoons

Converting between spoon standards is one multiplication and one division: multiply the tablespoon count by its mL value, then divide by the target tablespoon’s mL value.

Australian to US. 3 Australian tablespoons of butter is 3 × 20 = 60 ml. Divide by the US tablespoon: 60 ÷ 14.79 ≈ 4.06, so about 4 US tablespoons for every 3 Australian tablespoons a recipe calls for.

US to Australian. 4 US tablespoons of oil is 4 × 14.79 = 59.16 ml. Divide by the Australian tablespoon: 59.16 ÷ 20 = 2.96, which rounds to 3 Australian tablespoons (60 ml, about 1.4% over, close enough to ignore for a home kitchen).

A rough rule of thumb. Going from Australian tablespoons to US or metric tablespoons, multiply the spoon count by about 1.33 to 1.35, since 20 ÷ 15 = 1.33 and 20 ÷ 14.79 = 1.35 (roughly a third more spoonfuls needed for the same volume). Going the other way, from US or metric tablespoons to Australian, multiply by about 0.74 to 0.75, since 14.79 ÷ 20 and 15 ÷ 20 both land close to that figure (roughly a quarter fewer spoonfuls needed).

For anything more precise than a rough conversion, weigh the ingredient instead of counting spoonfuls. The recipe scaler keeps ingredient ratios consistent when resizing a recipe, and the guide to converting grams to cups covers how cup and spoon sizes vary by country in more detail.

Quick Reference

• US tablespoon: 14.79 ml (236.588 ml cup ÷ 16), rounded to 15 ml in everyday use.
• Metric tablespoon (UK, EU, Canada): 15 ml exactly.
• Australian tablespoon: 20 ml exactly, the outlier.
• Teaspoon: 5 ml everywhere in the metric world (4.93 ml in the US), unaffected by the tablespoon difference.
• 1 Australian tablespoon = 4 teaspoons. 1 US or metric tablespoon = 3 teaspoons.
• 15 ml tablespoon used on an Australian recipe: 25% under-measured.
• 20 ml Australian tablespoon used on a US or metric recipe: 33% over-measured.

When a recipe’s origin is unclear and the ingredient is small-volume and high-impact, such as baking powder or baking soda, weighing it in grams removes the guesswork entirely.