Cooking Conversion Calculator

Volume to volume: the conversions that never change

Volume converts to volume with a fixed factor, and that factor never changes. A cup is always 16 tablespoons, a tablespoon is always 3 teaspoons, and both are always the same number of milliliters. You can do these in your head once you know the chain.

The exact US values, taken from the NIST Handbook 44, Appendix C, are:

• 1 US cup = 8 fluid ounces = 236.588 milliliters
• 1 US tablespoon = 1/2 fluid ounce = 14.7868 milliliters
• 1 US teaspoon = 1/3 tablespoon = 4.92892 milliliters
• 1 US fluid ounce = 29.5735 milliliters

So 1 cup is 16 tablespoons and 48 teaspoons. Doubling a recipe that calls for 3 tablespoons gives 6, and the milliliter count doubles with it. None of this depends on what is in the cup.

Two details trip people up even inside the US system. Liquid measuring cups are marked to the rim for pouring, while dry measuring cups are meant to be filled and leveled, and swapping them matters for sticky things like honey or peanut butter. And while 1 cup of liquid does mean 8 fluid ounces, a "cup" of chopped vegetables has no reliable weight at all, because the answer depends on how big the pieces are. The general factors are set out in NIST Special Publication 811, which is the source manufacturers work from when they mark cups and spoons.

Volume to weight: the same cup holds different weights

Weight is a different story. A cup is a measure of space, and how much a cup of something weighs depends on how tightly it packs. There is no fixed factor between cups and grams, only a factor per ingredient. That is why a conversion chart has a column of numbers instead of one number.

The values below are the household portion weights published by USDA FoodData Central for one level US cup. They differ by more than four times from the lightest to the heaviest.

Granulated sugar weighs 200 / 125 = 1.6 times as much as the same cup of flour, and honey weighs 340 / 125 = 2.7 times as much. If a recipe gives you grams and you only have cups, you have to know which ingredient you are holding before you can convert.

The tablespoon trap: US, metric and Australian spoons

A tablespoon is the most common way to break a recipe in countries that do not use the US measuring set. Three different spoons are called a tablespoon, and they are not the same size.

The metric tablespoon is 15 - 14.7868 = 0.2132 mL bigger than the US one. Over a full cup that is 3.41 mL, or about 1.4 percent. Most baked goods survive that, because it sits inside the error of how you level a cup.

The Australian tablespoon is the one that ruins things. It is 20 - 14.7868 = 5.2132 mL larger, which is 5.2132 / 14.7868 = 35 percent more per spoon. Follow a US recipe with an Australian spoon and you are adding better than a third extra of every spooned ingredient. Check which spoon your set uses before you bake.

Worked example: converting 2 cups of flour

Here is the conversion the calculator runs with its default settings: 2 cups of all-purpose flour.

• To milliliters: 2 x 236.588 = 473.18 mL
• To fluid ounces: 473.176 / 29.5735 = 16 fl oz
• To US tablespoons: 2 x 16 = 32 tablespoons
• To teaspoons: 32 x 3 = 96 teaspoons
• To grams: 2 x 125 = 250 grams
• To ounces by weight: 250 / 28.3495 = 8.82 oz

Change the ingredient to granulated sugar and the volume stays at 473.18 mL, but the weight jumps to 2 x 200 = 400 grams. Same cup, same space, two different amounts of stuff. This is the one idea that separates cooks who trust a chart from cooks who trust a scale.

Scaling a recipe up or down without wrecking it

Scaling is where unit mistakes compound. Halving 3/4 cup is easier in tablespoons than in fractions: 3/4 cup is 12 tablespoons, so half is 6 tablespoons. The calculator prints the half amount for whatever unit you type.

• Work in the smallest unit. Convert to tablespoons or grams first, scale, then convert back. Rounding 0.375 cup to 0.4 cup loses accuracy that matters in baking.
• Scale weight, not volume, for flour. A cup of flour can swing from 115 g to 150 g depending on whether you scoop or spoon and level. Scaling in grams removes that error entirely.
• Leave salt, spice and leavener until last. Multiply them, then taste or check the rise. Doubling a recipe does not always mean doubling the cayenne.
• Pan size does not scale linearly. Doubling a batter needs a pan roughly 1.4 times wider, not twice as wide, because area grows with the square of the diameter.

Leaveners are the exception worth knowing. Doubling from one 8 inch pan to two 8 inch pans can double the baking powder. Moving that same batter to a 9 by 13 inch pan often needs slightly less, because the shape bakes differently. Whenever a conversion changes the pan, check the bake time as well, since a deeper pan wants a longer bake at a lower temperature.

When in doubt, write the whole recipe in grams once. Every later conversion becomes arithmetic instead of guesswork.

Oven temperatures and pan sizes

Oven temperatures convert with a formula, not a factor. Fahrenheit drops 32 degrees first, then scales by five ninths: 350 degrees Fahrenheit is 350 - 32 = 318, and 318 x 5 / 9 = 176.7 degrees Celsius, which every dial in the world rounds to 177.

The rows above cover the settings you use most. Fahrenheit drops 32 degrees first, then scales by five ninths, so 325 degrees Fahrenheit is 325 - 32 = 293, and 293 x 5 / 9 = 162.8 degrees Celsius. Gas marks are the UK scale, so use the Celsius column if your oven is electric.

Measuring by weight instead of by cup

Weighing ingredients fixes the problem that cups create. A digital scale costs about the same as a set of measuring cups, and it removes the two biggest sources of error in baking: how packed the cup is and which cup you grabbed.

• Flour: 125 g per cup is the standard, but scooped flour can hit 150 g. That is 20 percent more flour, which is why one person's cookie dough spreads and another's does not.
• Butter: 227 g per cup, and one stick is 113 g. If a US recipe says half a cup of butter, that is 114 g, close enough to the 113 g stick.
• Liquids: water is 237 g per cup and milk is 244 g per cup. Most recipes treat a cup of liquid as 240 mL, and the difference is too small to chase.

One habit makes it easier: put the bowl on the scale, press tare to zero, add the first ingredient, then zero it again for the next one. There is no arithmetic and nothing extra to wash. Most kitchen scales switch between grams and ounces with a button, so the numbers from this calculator work either way.

The catch is that most US recipes are written in volume, so you still need the chart to get started. Once you have the grams, weigh them every time after that.

Common conversion mistakes and how to check them

A few mistakes show up again and again. Each one is easy to check before you start mixing.

• Using a metric spoon for a US recipe. The Australian 20 mL spoon is 35 percent bigger, and that is enough to ruin a cake.
• Assuming a cup weighs 240 grams. That is true for water. It is wrong for flour by almost half, and wrong for salt and honey in the other direction.
• Scooping flour straight from the bag. Spoon it into the cup and level the top, or weigh it.
• Mixing up fluid ounces and ounces. A cup is 8 fluid ounces of space, but 8.4 ounces of water by weight. They are different units that share a name.
• Forgetting that a pint is 2 cups but a quart is 4. A quart of stock is 4 cups, and a gallon is 16 cups.

Check the units written on the recipe page too. A British recipe that says 1 cup usually means the metric cup of 250 mL, not the US cup of 236.588 mL. Australian recipes use that 250 mL cup alongside the 20 mL tablespoon, so treat those two as a set.

If a conversion feels off, run it through the calculator and check the unit label on the result line. Most kitchen disasters start with the right number next to the wrong unit.