One tablespoon is 3 teaspoons and half a fluid ounce

One US tablespoon is 3 teaspoons. In milliliters that is 14.78676478125 mL, because one teaspoon is 4.92892159375 mL and 3 x 4.92892159375 = 14.78676478125. In fluid ounces it is 0.5, since one fluid ounce is 6 teaspoons and 3 / 6 = 0.5.

NIST Handbook 44, Appendix C, 2026 edition, fixes the fluid ounce at 1/128 of a 231 cubic inch gallon and prints the exact SI equivalents. It also notes that the tablespoon and teaspoon are not legally defined units, so their milliliter values are rounded to the nearest milliliter in the reference tables. That single sentence explains the whole family of 15 mL spoons sold in stores.

Those five lines are the same quantity written five ways. Once you hold 3 and 0.5 in your head, the milliliter figure is a lookup and the cup figure is a division by 16.

The spoon ladder from a quarter teaspoon to a cup

Every kitchen conversion runs through the teaspoon. Half a tablespoon is 1.5 teaspoons, a quarter cup is 4 tablespoons, and a cup is 16 tablespoons or 48 teaspoons. The ladder below fills in the rungs that recipes do print, including the odd 1/3 cup that no spoon divides evenly.

The 1/3 cup row is the useful one. Five tablespoons is 15 teaspoons and 73.93382390625 mL, which leaves the measure 1 teaspoon short. Add that teaspoon and you reach 16 teaspoons, 78.8627455 mL, and the line on the cup. This is why so many recipes write 1/3 cup as 5 tablespoons plus 1 teaspoon instead of a decimal.

Butter: one stick is 8 tablespoons, 24 teaspoons, 113.4 grams

A US butter stick is 1/2 cup, 8 tablespoons, 24 teaspoons and 4 ounces by weight. Four ounces is 113.3980925 g, which wrappers print as 113.4 g. The paper is marked in tablespoon sections, so each mark is 1 tablespoon, 3 teaspoons and 14.175 g.

USDA FoodData Central entry 173410, SR Legacy release of April 2019, lists 1 tablespoon of salted butter at 14.2 g and one stick at 113 g. Multiply 8 x 14.2 and you get 113.6 g, so the per spoon and per stick figures disagree by 0.6 g. That is rounding in the database, not a different stick. Use the wrapper for a whole stick and the USDA spoon figure when a recipe asks for 1 or 2 tablespoons.

Three tablespoons of butter is 3/8 of a stick and 42.5 g, which is easier to hit on a scale than with a knife. If the recipe lists grams already, skip the paper marks entirely.

Half tablespoons, one and a half tablespoons and other odd amounts

Halves are where the tablespoon gets awkward. Half a tablespoon is 1.5 teaspoons and 7.393382390625 mL. One and a half tablespoons is 4.5 teaspoons and 22.180147171875 mL. Two thirds of a tablespoon is 2 teaspoons and 9.8578431875 mL. A quarter tablespoon is 3/4 teaspoon and 3.6966911953125 mL.

A worked scaling case: a cookie recipe uses 1 tablespoon of vanilla per batch and you are making 1.5 batches. Multiply 1.5 x 3 = 4.5 teaspoons. If the smallest spoon in the drawer is a 1/2 teaspoon, that is 4.5 / 0.5 = 9 scoops, which is a count you can do without a conversion at all.

The second case runs backward. A sauce calls for 2.5 tablespoons of cornstarch and you want to use a 1/2 tablespoon measure. Divide 2.5 / 0.5 = 5 level measures. In teaspoons the same amount is 2.5 x 3 = 7.5 teaspoons, and in milliliters 2.5 x 14.78676478125 = 36.966911953125 mL.

One more combination is worth memorizing: 1 tablespoon plus 1 teaspoon is 4 teaspoons, or 19.715686375 mL. It comes up in brine and spice rubs that call for a tablespoon and a splash.

A tablespoon of flour is not a tablespoon of water

A spoon measures space, not mass. A level tablespoon of all-purpose flour is about 7.8 g, because 125 g per cup divided by 16 is 7.8125 g. A tablespoon of granulated sugar is 12.5 g, from 200 / 16. A tablespoon of water is 14.78676478125 g, and honey is 21.0 g per tablespoon on the USDA portion list.

Where USDA lists a tablespoon portion directly, the table uses it: butter 14.2 g, milk 15.0 g and honey 21.0 g. Where it does not, the cup weight is divided by 16. Dry measures and liquid measures are built differently. A dry cup sits flush with the rim so you can sweep a knife across it. A liquid cup has a spout and lines below the rim, because you read the bottom of the meniscus at eye level. Using one for the other changes the pack. Flour scooped straight from the bag and leveled can weigh 10 g per tablespoon instead of 7.8 g, a 28 percent jump, and that is before anyone packs it.

The rule that saves a bake: spoon flour into the measuring spoon, then level it with the flat of a knife. Do not dip the spoon into the bag and do not tap it on the counter.

US, UK and Australian tablespoons: 14.79, 15 and 20 mL

The US tablespoon is 14.78676478125 mL. Most metric countries sell a 15 mL spoon, and modern UK recipes use that figure. Older British recipes used half an imperial fluid ounce, which is 17.7581640625 mL. Australia is the outlier: a metric tablespoon there is 20 mL, and it holds 4 teaspoons of 5 mL instead of 3.

The Australian spoon is 35.3 percent larger than the US one: (20 - 14.78676478125) / 14.78676478125 = 0.3526. One Australian tablespoon is 4.06 US teaspoons, since 20 / 4.92892159375 = 4.0577. A recipe from Sydney made with a US spoon comes up 26.1 percent short on every spoon of liquid, because 14.78676478125 / 20 = 0.7393.

The Australian figure is not folklore. Food Standards Australia New Zealand publishes the AUSNUT 2023 food measures file, and its tablespoon entries carry 20 mL for Australian foods while a cup is 250 mL. In the US, 21 CFR 101.9 lets a nutrition label call a tablespoon 15 mL, which is why the label spoon and the drawer spoon differ by 0.2 mL.

Medicine spoons, coffee scoops and the 15 mL label line

Liquid medicine is dosed in 5 mL teaspoons and 15 mL tablespoons, the same rounded values used on nutrition labels. A US kitchen teaspoon holds 4.92892159375 mL, so 3 kitchen teaspoons give 14.78676478125 mL, which is 0.21323521875 mL under a 15 mL dose. That is a 1.4 percent gap. It means nothing in a muffin batter and something in a child's fever reducer, so use the dosing cup that comes with the bottle.

A standard coffee scoop is 2 tablespoons, which is 6 teaspoons and 29.5735295625 mL, exactly 1 fluid ounce. If a recipe asks for 1 tablespoon of ground coffee and the only scoop in the drawer is that 2 tablespoon measure, fill it halfway. For a pot holding 12 cups of water at 1 scoop per 2 cups, the count is 6 scoops, or 12 tablespoons.

Half tablespoons show up on medicine cups as 7.5 mL. The true half tablespoon is 7.393382390625 mL, so the cup runs 0.107 mL high, again about 1.4 percent. A quarter tablespoon is 3.6966911953125 mL, and no medicine cup marks that, so measure 3/4 teaspoon instead.

The habit that covers all of these: read the unit on the recipe, match it to the spoon in your hand, and write the milliliter figure next to the line. A recipe card that says 1 tbsp and 15 mL side by side will survive any spoon you buy later.