1 cups to milliliters

One cup is 236.5882365 mL, the number taped inside the cabinet

A US cup holds 236.5882365 mL. The figure is the fluid ounce eight times over: one US fluid ounce is 29.5735295625 mL, and 8 x 29.5735295625 = 236.5882365. NIST Handbook 44, Appendix C (2026 edition) lists a measuring cup as 8 fluid ounces exactly and 237 milliliters, so the 237 in older books is this same value cut to a whole milliliter.

Three equivalences cover almost every US recipe card: 1 cup is 16 tablespoons, 48 teaspoons and 8 fluid ounces,. The BIPM SI Brochure (9th edition, 2019) confirms a milliliter is a cubic centimeter, which makes the metric side of the conversion exact arithmetic rather than a measured equivalence.

Doubling stays clean. Four cups are 946.3529 mL, and that quart is 53.6471 mL short of a liter. A liter is 4.2268 cups, so a European liter and an American quart land within six percent of each other.

Reading a jug: what each printed line means in cups

American jugs print ounces on one side and milliliters on the other, and the two scales never meet on a round number. A 500 mL jug marked every 50 mL moves in steps of 0.2113 cup, so each line is a fifth of a cup. The 250 mL line reads 1.0567 cups, and the 236.5882 mL line that would be exactly one cup is almost never printed.

Read the bottom of the curve rather than the edge where the liquid climbs the glass; on a wide 1 liter jug the two readings differ by 5 mL. Set the jug on the counter and read at eye level, once a hot liquid has settled.

A scale beats the lines for anything thick. Set the jug on the scale, press tare, and pour to the mass you want, 237 g for a cup of water or 244 g for a cup of whole milk. The Handbook 44 volume tables and the SI unit definitions agree on the size of the units, but neither tells you where the surface sits in your jug.

The fractions no measuring cup is marked for

Halves and quarters divide a cup evenly: 1/2 cup is 118.2941 mL and 1/4 cup is 59.1471 mL. Thirds do not. One third of a cup is 78.8627 mL, and no cup sold in the United States carries a 79 mL line, so the spoons take over.

One third of a cup is 5 tablespoons plus 1 teaspoon. Five tablespoons come to 73.9338 mL, and one more teaspoon at 4.9289 mL lands on 78.8627 mL. Two thirds is 10 tablespoons plus 2 teaspoons, or 157.7255 mL. A quarter cup is 4 tablespoons and a half is 8, so a spoon set covers almost any fraction.

Nutrition labels round the same fractions onto a coarser grid. 21 CFR 101.9(b)(5)(viii) sets a label cup at 240 mL, a tablespoon at 15 mL and a teaspoon at 5 mL, so a label third of a cup is 80 mL and a label half is 120 mL. The FDA guidance on metric equivalents repeats those round numbers for the household measure column on a package. A label third is 1.1373 mL larger than a kitchen third, about a quarter of a teaspoon.

Four cups wear the same name and differ by 20 percent

The word cup says nothing until you know the country. The US customary cup is 236.5882365 mL, and it is what a Pyrex cup sold in Ohio is marked in. The US legal cup is 240 mL, a nutrition label figure. The metric cup is 250 mL, the size a jug bought in Sydney or Berlin is graduated in. The imperial cup is 284.130625 mL, ten imperial fluid ounces, and it survives in British and Canadian books printed before the 1980s.

The metric cup bites hardest, because 250 mL looks round and a US cook reads it as one cup. Four metric cups of milk are 1,000 mL against 946.3529 mL for four US cups, so the same "four cups" is 53.6471 mL apart. In a sauce nobody notices, but in a cake the extra 5.67 percent is a different cake. The label definition and the NIST unit tables both make the distinction explicit, and the safe move is to convert the cup on the page where the recipe was written, then cook from milliliters.

One cup of flour does not weigh what one cup of water weighs

A cup is a volume, so its mass depends on what fills it. Water is the easy case: 236.5882 mL weighs 236.6 g at room temperature. Whole milk runs 1.03 g per mL, so a cup is 243.7 g. All purpose flour scooped from the bag is 0.53 g per mL, which puts a cup at 125 g in USDA FoodData Central and at 120 g on the King Arthur chart. Honey at 1.42 g per mL is 336 g a cup.

The flour row explains a lot of flat cakes. A cup scooped straight from the bag packs the powder against the wall and can weigh 150 g, a full 25 g over the 125 g the recipe assumed. Weighing the flour removes the variable, and the FDA metric equivalents exist on packaging for the same reason: a gram figure repeats, a packed cup does not.

Why a cereal box calls one cup 240 mL

Open a cereal box and the panel reads 1 cup (240 mL). The 240 is a legal definition, not a measurement: 21 CFR 101.9 fixes the label cup at 240 mL so every manufacturer rounds the same way. Two label cups are 480 mL while two real cups are 473.1765 mL, and across four cups the gap reaches 13.6471 mL, close to three teaspoons.

Label servings land on a coarser grid than kitchen fractions. A third of a label cup is 80 mL, two thirds is 160 mL, three quarters is 180 mL and a half is 120 mL. Set those against the kitchen values of 78.8627, 157.7255, 177.4412 and 118.2941 mL and the label version runs 1 to 2 mL high every time. For a custard or a brine, where the ratio of liquid to solids sets the result, the grams beside the household measure are the number to trust, and the FDA metric equivalent guidance says as much.

The practical rule: read the gram figure first, the milliliter figure second, and treat the cup in brackets as a courtesy. A 240 mL serving of milk is 247 g, not 240 g, which is why the panel prints both.

Small amounts: a 5 mL syringe, an espresso, a baby bottle

Under 50 mL the cup stops being useful and the teaspoon, the syringe and the bottle take over. A label teaspoon is 5 mL and a US customary teaspoon is 4.92892159375 mL, so half a teaspoon is 2.4645 mL on one system and 2.5 mL on the other. An espresso is 30 mL, or 0.1268 cup. A four fluid ounce baby bottle is 118.2941 mL.

Household spoons are not measuring spoons. Teaspoon capacities run from 3.5 to 6 mL depending on the pattern, so a 5 mL dose drawn with cutlery can be 30 percent high or 30 percent low. The dosing cup or oral syringe that ships with a liquid medicine is marked in mL for that reason, and the FDA household measure guidance keeps the 5 mL teaspoon on labels so the two systems can be compared at all.

Two small volumes worth memorizing: a metric drop is 0.05 mL, so 20 drops make 1 mL, and a standard shot of spirits is 44 mL. The NIST measuring device tables cover commercial dispensers at this scale, where a few milliliters separates a legal pour from a short one.

Quarts, gallons and liters worked backward into cups

Going up the scale is the same multiplication in reverse. Four cups are 946.352946 mL, one US quart. A gallon is 16 cups, and 16 x 236.5882365 = 3785.411784 mL. A half gallon of milk is 1892.705882 mL, and a 2 liter bottle is 8.4535 cups.

Liters convert with one division. One liter is 4.2268 US cups, 4.1667 label cups and exactly 4 metric cups. A 12 fluid ounce can is 354.8824 mL, which is 1.5 cups to the drop, the one place where a US can size and a cup count agree perfectly.

Rounding needs a rule or it compounds: 1 mL below 100 mL, 5 mL between 100 and 500 mL, 10 mL above that. Four cups rounded to 240 mL each come to 960 mL instead of 946.3529 mL, and that 13.6471 mL error is invisible in soup and visible in a brine. NIST Handbook 44 prints both the exact 8 fluid ounce cup and the rounded 237 mL figure for that reason: the exact value is for arithmetic, the round one for a printed scale. The SI Brochure closes the loop, since a liter is a cubic decimeter by definition.