How to convert volume units

Volume is where unit confusion gets expensive, because the US and UK gallon are different (US gallon = 3.785 L, UK gallon = 4.546 L) and neither is the liter, and cooking measures split further into fluid ounces that aren’t the same as weight ounces. Someone halving a British recipe in an American kitchen can easily be 20% off ingredient quantities without noticing why the cookies came out wrong. Shipping volumes use cubic feet and cubic meters, which require cubing linear conversion factors. Fluid versus dry measures in US cooking add another layer: a dry cup and a liquid cup have slightly different reference standards even though most people use them interchangeably. This guide covers metric volume, US and UK imperial volume, cooking measurements, US vs UK gallons, fluid vs dry distinctions, and the cubic volume calculations that come up in shipping and construction.

Metric volume

1 cubic meter (m³) = 1,000 liters (L) = 1,000,000 mL = 1,000,000 cm³
1 liter (L)        = 1,000 mL = 1,000 cm³ = 1 dm³
1 mL               = 1 cm³
1 kL (kiloliter)   = 1,000 L = 1 m³

A liter is defined as exactly one cubic decimeter (10 cm on each side). One milliliter equals one cubic centimeter exactly—this equivalence is why medical dosing and lab work use cc and mL interchangeably. For water at 4 °C, 1 mL weighs exactly 1 g, making water the mental calibration point between mass and volume.

US imperial volume

1 US gallon (gal)   = 4 quarts (qt) = 8 pints (pt) = 16 cups = 128 fl oz
1 quart             = 2 pints = 4 cups = 32 fl oz
1 pint              = 2 cups = 16 fl oz
1 cup               = 8 fl oz = 16 tbsp = 48 tsp
1 fluid ounce (fl oz)= 2 tbsp = 6 tsp
1 tablespoon (tbsp) = 3 teaspoons (tsp) = 0.5 fl oz

Exact: 1 US gallon = 3.785411784 L

UK imperial volume

1 UK gallon = 4 UK quarts = 8 UK pints = 160 UK fl oz
1 UK pint   = 20 UK fl oz   (not 16!)
1 UK fl oz  = 28.4131 mL    (not 29.5735 like US)

Exact: 1 UK gallon = 4.54609 L

Gallons: US 3.785 L vs UK 4.546 L — differ by 20%
Pints:   US 473 mL vs UK 568 mL — differ by 20%

The US pint is 16 fluid ounces; the UK pint is 20 fluid ounces. The US fluid ounce and UK fluid ounce are also slightly different sizes. For beer, wine, and home recipes, a 20% difference is huge. Always check whether a recipe or a pub is using US or UK measures.

Metric ↔ US imperial

1 US gallon = 3.7854 L
1 L         = 0.2642 US gal
1 US qt     = 0.9464 L     (close to a liter!)
1 US cup    = 236.6 mL
1 US fl oz  = 29.5735 mL
1 tbsp      = 14.787 mL
1 tsp       = 4.929 mL     (commonly rounded to 5 mL)

Memorable:
  1 quart ≈ 1 liter (off by 5%)
  1 cup ≈ 240 mL (off by 1.5%)
  1 tbsp ≈ 15 mL
  1 tsp ≈ 5 mL

Fluid ounces vs weight ounces

A fluid ounce measures volume; a weight ounce measures mass. For water, 1 fl oz weighs about 1 oz (the system was designed around this). For denser liquids (honey, syrup) 1 fl oz weighs more; for lighter (alcohol, oil) it weighs less. “8 ounces” on a nutrition label is weight; “8 ounces” on a measuring cup is volume. They coincide numerically only for water.

Dry vs liquid measures (US cooking)

US cooking has two cup standards. The liquid cup (8 fl oz = 237 mL) is designed with a spout for pouring. The dry cup (also ~237 mL in volume but defined by the “level off” measure) is used for flour and sugar. In practice, the volumes are equivalent; the shape differs so dry ingredients can be leveled with a knife. Some older references cite a 231 vs 237 mL distinction, but modern usage treats them as the same 237 mL.

Cubic volume

For 3D volumes (shipping, construction, tank sizes), remember to cube the linear conversion factor.

1 ft³     = 0.02832 m³
1 m³      = 35.315 ft³
1 yd³     = 27 ft³ = 0.7646 m³

A box 2 ft × 3 ft × 4 ft = 24 ft³ = 0.68 m³
Not 24 × 0.3048 = 7.3 m³ (off by a factor of 35)

Cooking conversion table

1 tsp    = 5 mL          (approximate)
1 tbsp   = 15 mL = 3 tsp
1/4 cup  = 60 mL = 4 tbsp
1/3 cup  = 80 mL
1/2 cup  = 120 mL
1 cup    = 240 mL
2 cups   = 480 mL (about 1 pint)
4 cups   = 950 mL (about 1 quart ≈ 1 L)
1 gallon = 3.8 L

Shipping dimensions

Shipping companies use cubic feet or cubic meters for volume, sometimes billed as dimensional weight (volume-based pricing). A 1 m³ container holds about 35.3 ft³. An intermodal shipping container (20-foot) holds about 33 m³ of cargo. Freight quotes usually require length, width, height in the same unit; convert before multiplying.

Fuel and chemicals

Gasoline is sold by the US gallon in the US, by the liter almost everywhere else. Jet fuel is measured in US gallons, Imperial gallons, and liters depending on the airport, and sometimes by weight (pounds or kilograms) for flight planning. Industrial chemicals often come in 55-US-gallon drums (208 L) or 200-liter drums (53 US gal)—different containers despite similar appearance.

Medical dosing

Medical contexts use mL and cc interchangeably (they’re identical by definition). Drops (gtt) are roughly 0.05 mL, so 20 drops ≈ 1 mL, but this varies with dropper design. Never substitute volume for a weight-based dose (mg per kg) without knowing the concentration—a 1 mL pediatric dose of acetaminophen can be 100 mg or 160 mg depending on the formulation.

Fluid dram and minim

Older pharmaceutical and apothecary texts use fluid drams (1 fl dr = 1/8 fl oz = 3.7 mL) and minims (1/60 fl dr = 0.062 mL). These are obsolete in modern practice but still appear on antique bottles and in historical recipes.

Common mistakes

Using US gallons when a recipe calls for UK gallons (or vice versa). The 20% difference breaks recipes and inflates fuel bills. Always confirm the origin of the measurement.

Applying linear conversion to cubic volume. 1 m = 3.28 ft, but 1 m³ = 35.3 ft³ (cube the factor). Linear conversion of a volume is off by a factor of ~11.

Confusing fluid ounces with weight ounces. They’re numerically equal only for water. For honey, oil, or flour, the weight and volume ounces diverge.

Mixing US and UK pints. A US pint is 473 mL; a UK pint is 568 mL. Order a pint in London, you get more beer than in New York.

Using volume for baking precision. A cup of flour ranges from 110 g to 150 g depending on scoop technique. Weight measurements are reproducible; volume isn’t.

Forgetting tablespoons and teaspoons aren’t universal. Australian tablespoons are 20 mL (not 15); Canadian and UK tablespoons are 15 mL. Recipes from Australia need adjustment.

Misreading a gas mileage conversion. US MPG and UK MPG differ because the gallons differ. 30 MPG (US) is 36 MPG (UK) is 7.84 L/100km. European and North American fuel economy numbers are not directly comparable without converting.

Run the numbers

Stop guessing whether a recipe means US or UK; drop your value into our volume converter and get every standard unit at once. Pair it with the cooking converter for recipe-specific conversions involving weight and volume together, and the weight converter for the flour-by-cup versus flour-by-gram problem.