How this instrument works
Every US liquid gallon holds exactly 231 cubic inches, an odd-looking figure inherited from Queen Anne's wine gallon of 1707. That vessel was described in statute as a cylinder seven inches across and six inches deep, whose true capacity works out to 230.907 cubic inches; legislators rounded up to 231 and nobody has disturbed it since. Congress kept that wine gallon when Britain scrapped its own in 1824 for imperial measure, which is how American and British volumes parted company.
Quart descends from Latin quartus by way of Old French quarte — one quarter part. Its factor is therefore named rather than measured: four quarts constitute one gallon by definition, much as twelve inches constitute one foot. Because treaty work in 1959 pinned an inch at 25.4 mm precisely, both vessels also carry exact metric capacities — 3.785411784 L per gallon, 0.946352946 L per quart, which is 57.75 cubic inches.
Americans still buy milk by gallon and half gallon, motor oil and paint by quart. A quart of interior latex covers roughly 100 square feet against about 400 for a gallon, and most passenger-car engines take four to six quarts of oil. Shops quote five quarts rather than 1.25 gallons for good reason: quarts tend to land on whole numbers where gallons will not.
- Type your volume into US gallons (gal) — a 5 gal starting value is already loaded.
- Read Quarts (qt) directly beneath; that line recomputes as you type, to six decimal places.
- Going backwards? Divide your quart figure by 4 and enter that result in US gallons (gal).
- Check which gallon you actually hold: this sheet works in US liquid measure, not imperial gallons still quoted in Britain and Canada.
Worked example — five gallons into quart jars
One small cidery racks 5 gallons into its carboy and needs to know how many quart jars that fills. Enter 5 into US gallons (gal), and Quarts (qt) returns 20.0. Twenty jars, no awkward remainder, because five fours land squarely on whole numbers.
Arithmetic behind that answer deserves a second look. Five gallons is 1155 cubic inches (5 × 231), and 1155 ÷ 57.75 comes to 20 with nothing left over. Multiplying by 4 also happens to be one operation binary floating point never fudges — it bumps an exponent by two and leaves every significant digit untouched — so 20.0 really is twenty, not 19.999999.
Questions
Is a gallon exactly 4 quarts?
Yes, exactly — and by definition rather than by measurement. Quart names a quarter part, so four of them constitute a gallon with zero uncertainty, in every system that uses both words. US liquid, US dry, and British imperial measure all keep that same 4:1 ratio internally. What differs between those systems is how big each vessel actually is, never how many quarts fill its gallon.
Is a US quart the same as an imperial quart?
No, and confusing them is far and away a common error here. A US liquid quart is 0.946352946 L; an imperial quart, still used informally in Britain and Canada, is 1.1365225 L — roughly 20% larger. Their gallons differ by that same ratio: 3.785411784 L against 4.54609 L. Both remain four quarts to a gallon, so this sheet's factor holds either way, but a British recipe calling for two quarts of stock wants nearly half a litre more liquid than an American one.
What about dry quarts for berries and produce?
Dry measure is a separate family, descended from a Winchester bushel of 2150.42 cubic inches rather than from Queen Anne's wine gallon. A US dry quart works out to 67.200625 cubic inches, about 1.101 L, roughly 16% larger than its liquid namesake — which matters when strawberries or oysters are sold by dry quart. Four dry quarts still make a dry gallon, but do not use figures from this converter for produce sold that way.
How many cups and fluid ounces are in a quart?
A US liquid quart contains 2 pints, 4 cups, or 32 US fluid ounces. Scaling up, one gallon holds 4 quarts, 8 pints, 16 cups, and 128 fluid ounces. Every one of those relationships is exact whole-number bookkeeping, so a half-gallon jug is 2 quarts or 64 fluid ounces without qualification. Note that a US fluid ounce and a British one differ slightly, at 29.5735 mL against 28.4131 mL.
What does a quart of water weigh?
About 2.086 pounds, or 0.946 kg, near room temperature — and unlike your quart figure itself, that weight is approximate. Water density shifts with temperature and dissolved content, peaking around 4 °C, so any volume-to-weight step carries real uncertainty that a ×4 conversion does not. A gallon of water runs about 8.345 pounds, which is where the old rhyme "a pint's a pound" comes from; it holds tolerably well for US pints and not at all for imperial ones.