1 teaspoon = 4.9289 millilitres. Cups, spoons, pints and litres are all measures of the same thing — volume — and this page converts between two of them. The factor is fixed by definition, not measured in a kitchen, so it is the same for every ingredient, every recipe and every brand of measuring cup. What follows is the full table for the amounts you actually cook with, worked examples from real recipes, and the mistakes that catch people out even when the maths is right.
The reason this conversion is worth a page of its own is that it sits at the junction of two measuring traditions. The US customary system grew out of old English measures, while the metric system was designed to be decimal — and recipes cross between them constantly now that cooks follow recipes from every country on the internet. Knowing that 1 teaspoon is a fixed number of millilitres means you can follow any recipe, whatever system it was written in, with the tools you already own.
Conversion table
| Teaspoons | Millilitres |
|---|---|
| 1 teaspoon | 4.9289 millilitres |
| 2 teaspoons | 9.8578 millilitres |
| 3 teaspoons | 14.7868 millilitres |
| 4 teaspoons | 19.7157 millilitres |
| 6 teaspoons | 29.5735 millilitres |
| 9 teaspoons | 44.3603 millilitres |
| 12 teaspoons | 59.1471 millilitres |
| 24 teaspoons | 118.2941 millilitres |
| 48 teaspoons | 236.5882 millilitres |
Read the table in either direction. Going from teaspoons to millilitres, multiply by 4.9289; going back, divide by 4.9289 or multiply by 0.2029. The middle rows are the ones recipes use most — 4 teaspoons is 19.7157 millilitres, and 9 teaspoons is 44.3603 millilitres. If your amount is not in the table, multiply it by 4.9289 and you have the answer. For a quick check: 1 teaspoon is 4.9289 millilitres, 2 teaspoons are 9.8578 millilitres, and 10 teaspoons are 49.2892 millilitres.
Worked examples
Checking a measuring jug. Jugs are not always honest. Pour 3 teaspoons of water into the jug — that should read 14.7868 millilitres on the millilitres scale. If it reads noticeably more or less, trust the teaspoons: measuring cups and spoons are made to a standard, while cheap jugs are often printed a few percent out. A jug that is wrong by 5% will put 5% too much liquid in every cake, soup and sauce you make with it, which is enough to notice.
Working from a video recipe. The cook on screen measures 3 teaspoons and your set only has a millilitre measure. That is 14.7868 millilitres — pause the video, count them out, and carry on. Video recipes are the worst for mixed units, because the cook never stops to convert for you. Keep this page open on your phone while you cook and the pause button becomes your conversion chart.
A recipe written in the other system. You find a lemon drizzle cake recipe from a metric cookbook that lists 59.1471 millilitres, but your measuring cups are marked in teaspoons. That is 12 teaspoons — a familiar measure again. This is the most common reason people look this conversion up mid-cook: one recipe, two measuring systems, and dinner in an hour. Convert the whole recipe to one system before you start, write the converted amounts on the page, and you will not have to do the arithmetic with wet hands.
How the conversion works
The US teaspoon is defined as 4.9289 ml, and the millilitre is defined as 1 ml. Divide the first by the second and you get 4.9289 — that is the whole derivation, and it is why the conversion is exact rather than approximate. No kitchen experiment was needed to establish it; the units were defined this way, so the ratio follows from the definitions. That is also why the same factor appears in every reliable conversion chart: there is only one right answer, and every source that uses US customary units agrees on it.
The one thing to check is which teaspoon your recipe means. This page uses the US customary teaspoon throughout. A metric cup is 250 ml, an imperial cup is 284 ml, and older recipes sometimes use a 'cup' that means whatever cup the writer had in the cupboard. If a recipe from outside the US gives an amount that looks wrong after converting — a cake with far too much liquid, a soup that is far too thin — the cup is the first suspect. Convert the recipe to grams once, write the grams on the recipe card, and the question never comes up again.
Rounding deserves a note too. The exact factor is 4.9289 to four decimal places, and the full value runs further (4.93 ml divided by 1.00 ml). For everyday cooking, rounding to two or three significant figures is fine: a 1% rounding error is invisible in a soup and barely noticeable in a cake. But round only at the end. If you round the factor and then multiply by a large amount, the rounding error grows with the amount — so keep the full factor through the calculation and round the answer, not the factor.
Volume is not weight
A conversion between two volume units is the same for every ingredient, but a conversion between volume and weight is not — and confusing the two is the most common conversion mistake in cooking. A cup of all-purpose flour weighs about 120 g spooned and levelled (King Arthur Baking), a cup of granulated sugar about 198 g, a cup of butter about 227 g, a cup of milk about 244 g (USDA), and a cup of honey about 336 g. All of those weights are approximate, because they depend on how the ingredient is measured: flour is spooned and levelled, brown sugar is packed at about 213 g a cup, and honey is poured.
Flour weight is the most disputed conversion in baking. King Arthur Baking lists 120 g per cup spooned and levelled, while other sources quote 125 g, 130 g and up to 142 g for a scooped cup. We use the King Arthur spooned-and-levelled value as primary, and the gap is a warning: if you scoop flour instead of spooning and levelling it, you can add 20 g or more per cup, which is enough to make a cake dry. Granulated sugar carries a smaller dispute — King Arthur lists 198 g per cup and the USDA rounds it to 200 g, a difference of rounding rather than a real disagreement. When a recipe matters, verify with a kitchen scale: weigh the ingredient instead of measuring it by volume, and every dispute on this page disappears.
Measuring accurately
The conversion is exact, so any error in your cooking comes from the measuring, not the maths. Use a liquid measuring jug for liquids and dry cups for dry ingredients — a jug's wide top and spout make it hard to level a dry ingredient, and a dry cup's flat rim makes it hard to read a liquid meniscus. Read a jug at eye level, on a flat surface, with the liquid settled; reading it from above makes the meniscus look higher than it is. For spoon measures, level with the back of a knife: a heaped spoon can hold half as much again as a level one, which is a 50% error in a teaspoon of baking powder. Measure over the sink or the ingredient's own container, never over the mixing bowl, so a spill does not go into the batter. And if you own a kitchen scale, use it for anything that matters — weighing is more accurate than any volume measure, and it removes the conversion entirely. Keep your measuring cups together as a set, because cups from different sets are not always the same size, and a mixed set is a quiet source of error in every recipe you cook.
Frequently asked questions
Is a US teaspoon the same as a metric or imperial teaspoon?
Not always, and this is the biggest trap in unit conversion. This page uses the US teaspoon (4.9289 ml). A metric cup is 250 ml, an imperial cup is 284 ml, a US pint is 473 ml while an imperial pint is 568 ml, and an Australian tablespoon is 20 ml against the US 14.79 ml. If your recipe comes from outside the US, check which system it uses before converting — the factor on this page is correct for US measures only.
Can I use a kitchen scale instead of converting?
For liquids, often yes. A kitchen scale removes volume conversion entirely if the recipe gives grams, and for water-based liquids 1 ml weighs about 1 g, so millilitres and grams are nearly interchangeable. But the shortcut fails for fats and syrups: a cup of olive oil weighs about 216 g, not 237 g, and a cup of honey about 336 g. Use the scale when the recipe gives weights, and use this conversion when the recipe gives volumes.
Does temperature change the conversion?
No, not in any way that matters in a kitchen. Liquids expand slightly when heated, so a cup of boiling stock is a fraction of a percent larger in volume than a cup of cold stock, but the difference is far smaller than ordinary measuring error. Measure liquids at room temperature where you can, and never worry about temperature when converting between volume units.
How many teaspoons are in 1 millilitre?
0.2029 teaspoon — the reverse of the main conversion. Divide the number of millilitres by 4.9289, or multiply by 0.2029. For example, 0.8115 teaspoon is 4 millilitres. Use the reverse direction when a metric recipe gives you millilitres and your cups are in teaspoons.
How do I convert teaspoons to millilitres without a calculator?
Multiply by 4.9289; for a quick mental estimate, round the factor to a friendly number and accept a small error. If the factor is larger than 1, break the amount into whole units and fractions — for example, convert 2 teaspoons and a half teaspoon separately and add them. If the factor is smaller than 1, remember that one millilitre is 0.2029 teaspoon, which is often easier to picture. For anything that matters, a phone calculator or the table on this page is faster and more accurate than mental maths mid-recipe.