How this instrument works
The US gallon is 231 cubic inches — exact, by statute. That odd number is an inheritance: it approximates Queen Anne's wine gallon of 1707, described as one cylinder seven inches across and six inches deep, whose true volume works out near 230.907 cubic inches. Legislators preferred round figures, so 231 it became. When Congress standardised Treasury measures in 1832 it kept that wine gallon — eight years after Britain had abandoned it for the larger imperial gallon defined by ten pounds of water.
Pints come from halving. Cut one gallon in two for the pottle; halve again for the quart, so named because it takes one quarter of the gallon; halve once more and you reach the pint, whose name traces to Old French pinte and probably to measure marks painted down each vessel's side. Three halvings make eight. Keep going and you meet cups, then gills. Because 8 counts subdivisions rather than measuring anything, it survives every gallon ever legislated: imperial, US liquid, and US dry each pour eight pints.
Metric equivalents follow from 1 inch = 25.4 mm, so one US gallon is 3.785411784 litres exactly and one US liquid pint 473.176473 millilitres. Both units turn up daily across America — milk in plastic gallon jugs, ice cream in pint tubs, beer served in 16-ounce glasses, paint mixed by quart and gallon, homebrew fermenting in five-gallon carboys that yield forty pints. Whole-blood donation, at roughly 470 to 500 mL, sits near enough to one pint that donors have called it that for over 100 years.
- Type your volume into the US gallons (gal) field; it opens at 2 gal for reference.
- Read your answer on the Pints (pt) line, recomputed as you type and carried to six decimals.
- Working backwards from pints? Divide by 8 and enter that figure — 24 pt goes in as 3 gal.
- Need quarts or cups instead? Quarter your gallon figure for quarts, or double the pint figure for cups.
- Check whether your recipe means US pints or imperial ones; British pints run about 20% larger.
Worked example — two gallons into pint tubs
One small creamery finishes its 2-gallon batch of custard base and wants to know how many retail tubs that fills. Enter 2 into US gallons (gal); Pints (pt) reads 16.0. Sixteen tubs, none left over, because gallons split into pints by whole numbers.
Two independent checks agree. By ounces: 2 gallons is 256 US fluid ounces, each pint holds 16 of them, and 256 ÷ 16 = 16. By volume: 2 × 231 = 462 cubic inches, or 7.570823568 litres, divided by 473.176473 mL per pint — 16 again, to the final digit.
Questions
Is 8 pints per gallon exact, or rounded?
Exact. Pints are defined as one eighth of gallons, so 8 counts parts rather than measuring volume; it carries no uncertainty at any number of decimals. Nothing underneath rounds either: 3.785411784 L per US gallon and 473.176473 mL per pint are both exact figures, descending from 231 cubic inches and from 1 inch = 25.4 mm.
Does this also work for imperial (UK) gallons?
That count does; those sizes do not. An imperial gallon likewise splits into 8 imperial pints, so multiplying by 8 gives correct answers in imperial pints. But imperial gallons hold 4.54609 L against 3.785411784 L for US ones, and each imperial pint holds 568.26125 mL — so 2 imperial gallons pour 16 pints containing roughly one fifth more liquid than 16 US pints. Never pair US gallons with British pints.
What about US dry pints and dry gallons?
Same factor, different vessel. The US dry gallon is 268.8025 cubic inches — one eighth of the Winchester bushel — and splits into 8 dry pints of about 550.6 mL. Berries, shellfish and grain are still sold that way. This sheet handles liquid measure only, so dry quantities treated as liquid come out roughly 16% low.
How many fluid ounces and cups is that?
US pints hold 16 fluid ounces and 2 cups, so each gallon carries 128 fluid ounces and 16 cups. Multiply your gallon figure by 128 for ounces or by 16 for cups. British measure diverges twice over: UK pints hold 20 imperial fluid ounces, and the imperial fluid ounce is itself smaller at 28.4131 mL against 29.5735 mL.
Why is the gallon 231 cubic inches?
Because one rounded approximation got frozen into law. Queen Anne's 1707 wine gallon was described by its geometry: one cylinder 7 inches wide and 6 inches deep. That shape yields about 230.907 cubic inches, and 231 was tidier. Britain dropped that vessel in 1824 for its own gallon, pegged to ten pounds of water, but American practice had already settled, and 231 has stood ever since.
Does one pint of water really weigh one pound?
Close, though slightly over. US pints of cool water weigh about 1.043 lb, which is why "a pint's a pound the world around" survives as kitchen shorthand. Britain fares worse: imperial pints of water run near 1.25 lb, and older rhymes there admit it. Density shifts with temperature and with whatever is dissolved, so weigh anything that matters rather than assuming.