Butter Calculator

Background.

A stick of butter is a quarter of a pound, and every other US butter measurement follows from that one fact: 4 ounces, 8 tablespoons, half a cup, 113.3980925 grams at NIST's exact pound of 453.59237 g. This calculator takes any of those units, plus pats, teaspoons, grams and pounds, and reports all of them at once, along with the milkfat and water the amount contains from USDA FoodData Central's analysis of salted butter.

The reason it needs to exist as a separate page rather than as a row in a unit converter is worth stating plainly, because it is the same reason the two conversion pages on this site decline the job. Sticks, tablespoons, cups and pats are volume or count measures; grams, ounces and pounds are mass. Crossing between them requires the density of the substance in the cup. The site's cooking converter refuses that crossing by design and says so in its own FAQ — "the calculator will reject a cross-category conversion such as cup to gram because the answer depends on the density of the ingredient, which the calculator does not know" — and it names butter specifically as the example. The general unit converter has no stick unit at all, and its category selector makes mass-to-volume structurally impossible. This page is the density-aware reference both of them point at.

There is one complication that most butter conversion charts paper over, and this page surfaces it instead. USDA publishes four butter portions: a pat at 5 grams, a tablespoon at 14.2, a stick at 113 and a cup at 227. Those four numbers are not mutually consistent, because a stick is eight tablespoons and half a cup by definition. Eight tablespoons of 14.2 grams is 113.6, not 113. Two sticks of 113 grams is 226, not 227. Sixteen tablespoons is 227.2, not 227. And 113 grams is not a quarter pound, which is 113.398. Every figure is a three-significant-figure rounding of a related quantity, and rounding four related quantities independently is exactly how a table stops closing. None of them is wrong; they cannot all be exact at once.

So the calculator ships both bases as a choice rather than picking one quietly. The quarter-pound basis is the default because it is internally exact — one stick returns precisely 4 ounces, precisely 0.25 pounds, precisely 8 tablespoons, precisely 24 teaspoons and precisely half a cup, which are the five identities printed on the wrapper — and because the quarter-pound stick is how US butter is actually sold. The USDA basis is there for anyone reconciling against a USDA nutrition figure, where matching their portion weight matters more than internal consistency. Whichever you pick, the page tells you what the other one would have said. The spread is never more than about half a percent, which is under a gram on a stick, but it is visible rather than buried.

Two scope limits belong beside the answer. The composition figures are for salted butter and they are analytical means, not specifications: 81.11 percent milkfat and 16.17 percent water. Unsalted butter has a different water content, and USDA's unsalted entry could not be retrieved when this page was built, so no butter-type selector and no sodium figure ship rather than an estimate being invented. And "European-style" butter is not modelled at all — it is a marketing description, not a standard of identity. The only statutory floor is the 80 percent milkfat in 21 U.S.C. 321a, which Codex Alimentarius matches internationally, and there is no citable figure for an 82 or 84 percent product.

What is butter calculator?

Butter is a water-in-oil emulsion of milkfat, water and a small fraction of milk solids, and both US statute and international standard set the same floor for it: 21 U.S.C. 321a, on the books since 1923, defines butter as made exclusively from milk or cream "and containing not less than 80 per centum by weight of milk fat", and Codex Alimentarius CXS 279-1971 sets a minimum of 80% milkfat with a maximum of 16% water and 2% milk solids-not-fat.

The US retail stick is a quarter pound. That is the origin of every awkward-looking butter number in an American recipe: the stick is 113.4 g, and because it is also marked in eight tablespoons and half a cup, a tablespoon of butter is a thirty-second of a pound, 14.17 g. Four sticks make the one-pound box.

USDA FoodData Central's SR Legacy entry for salted butter gives the composition this page reports: 81.11 g of total lipid and 16.17 g of water per 100 g, plus household portions for a pat, a tablespoon, a stick and a cup.

The range of validity is solid, packed, salted butter in US retail units. It is exact arithmetic on published constants. What it does not cover: unsalted butter's different water content, sodium, clarified butter and ghee, cultured or so-called European-style butters with no citable composition, whipped butter (a different bulk density entirely), melted butter measured by volume, and margarine or any other spread, which is not butter under either the US statute or the Codex standard.

How to use this calculator.

1. 01Enter the amount of butter you have or need, and pick the unit it is in. There is no target unit to choose — every unit is reported at once.
2. 02Leave the mass basis on the quarter-pound stick unless you have a reason not to. It is the internally exact one: a stick comes back as precisely 4 ounces, 8 tablespoons and half a cup, which are the numbers printed on the wrapper.
3. 03Switch to the USDA basis when you are reconciling a quantity against a USDA nutrition figure and want their published portion weight rather than the arithmetically exact one. The page will tell you what the other basis would have said either way.
4. 04Read the milkfat figure if a recipe is fat-sensitive — pastry, shortbread, laminated dough. It uses USDA's analytical mean of 81.11 percent, and the legal-minimum figure beside it shows the least fat a legal butter of that weight can contain.
5. 05Treat the water figure as an average, not a limit. Codex caps butter water at 16 percent while USDA's measured mean is 16.17, so the two published numbers do not quite agree and the page says so rather than picking one.
6. 06For a European 250 g block, enter 250 grams. It comes out at 2.20 sticks and 1.10 cups — which is why a US recipe written in sticks cannot be followed from a European block by eye.
7. 07If you are substituting oil for the butter rather than re-measuring it, use the oil-to-butter calculator instead: that is a change of ingredient, and it removes water that this page will not tell you to replace.

The formula.

The whole page is one multiplication followed by seven divisions. The entered amount is multiplied by the grams-per-unit figure for its unit, giving the mass in grams, and then that mass is divided by every other unit's own figure.

Where the constants come from on the default basis. NIST SP 811 fixes the avoirdupois pound at exactly 453.59237 g and the ounce at exactly 28.349523125 g. The US butter stick is a quarter pound, so a stick is 453.59237 / 4 = 113.3980925 g. The wrapper marks the stick in eight tablespoons, so a tablespoon is 453.59237 / 32 = 14.1747615625 g. Two sticks make a cup, so a cup is 226.796185 g. The teaspoon is not published for butter by any source consulted, so it is derived from the exact NIST identity that a tablespoon is three teaspoons: 453.59237 / 96 = 4.7249205208 g. The pat is USDA's 5 g. Every identity on the wrapper then falls out exactly rather than approximately, which is the check that the constants are right: one stick returns 4.0000000000 ounces, 0.2500000000 pounds, 8.0000000000 tablespoons, 24.0000000000 teaspoons and 0.5000000000 cups.

On the USDA basis the four portion weights are used as published — pat 5 g, tablespoon 14.2 g, stick 113 g, cup 227 g — with the teaspoon again derived as a third of the tablespoon, and the ounce and pound still from NIST because USDA does not publish those for butter. Those four figures do not close, and the calculator does not pretend otherwise: on that basis a stick is 7.9577464789 tablespoons and 0.4977973568 cups, not 8 and 0.5. If you see those numbers, the USDA basis is selected and it is behaving correctly.

Composition is three more multiplications on the gram figure: 0.8111 for USDA's analytical fat mean, 0.80 for the statutory minimum in 21 U.S.C. 321a, and 0.1617 for USDA's water mean. At 100 g those read straight off as 81.11, 80 and 16.17. The remainder, 2.72 g, is milk solids-not-fat plus salt, which is why Codex's 2 percent solids cap and a salted-butter analytical mean are not directly comparable quantities.

Rounding stage. Nothing is rounded at an intermediate step. Every quantity is carried in arbitrary-precision decimal arithmetic and rounded exactly once, at the point the result leaves the calculator, to ten decimal places. That is what allows the five wrapper identities to come back exact rather than as 7.9999999998 tablespoons.

Classification stage. This page classifies nothing. Every numeric output is the same butter expressed in a different unit or a composition fraction of it, and the two text outputs name the basis and its source without attaching a verdict to any number. There is therefore no band edge anywhere that could be decided from a rounded value. What is tested instead is the exactness set: one stick must return exactly 4 oz, 0.25 lb, 8 tbsp, 24 tsp and 0.5 cups on the quarter-pound basis, and must return 7.9577 tbsp and 0.4978 cups on the USDA basis — the second asserted as explicitly not 8 and not 0.5, so a silent basis swap fails the test suite instead of shipping.

A worked example.

Frequently asked questions.

References& sources.

1. [1]U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, SR Legacy entry FDC ID 173410, "Butter, salted"; retrieved 30 July 2026 through the FoodData Central REST API endpoint /v1/food/173410. The source of every composition and portion figure on this page: total lipid (fat) 81.11 g per 100 g (580 data points); water 16.17 g per 100 g (7 analytical samples, range 15.8 to 16.61 g); and the household portions 1 pat (1 inch square, 1/3 inch high) = 5 g, 1 tablespoon = 14.2 g, 1 cup = 227 g, 1 stick = 113 g. Those four portion weights are the USDA mass basis offered on the page, and their mutual inconsistency is documented in the basis note. Independence: primary. Access: open.
2. [2]United States Code, Title 21, Section 321a — "Butter" defined (enacted 4 March 1923, 42 Stat. 1500); retrieved 30 July 2026 from the Cornell Legal Information Institute's reproduction of the US Code. Quoted verbatim for the statutory floor this page reports as the legal-minimum milkfat figure: butter is "the food product usually known as butter, and which is made exclusively from milk or cream, or both, with or without common salt, and with or without additional coloring matter, and containing not less than 80 per centum by weight of milk fat, all tolerances having been allowed for." Independence: primary. Access: open.
3. [3]National Institute of Standards and Technology. NIST Special Publication 811, 2008 edition — Guide for the Use of the International System of Units (SI). Table B.8, avoirdupois mass: the pound is exactly 453.59237 g and the ounce exactly 28.349523125 g. Every ounce and pound figure on this page comes from these values, as does the whole quarter-pound-stick basis: a stick is 453.59237 / 4 = 113.3980925 g, a tablespoon 453.59237 / 32, a cup 453.59237 / 2, and the teaspoon is derived as a third of the tablespoon using the exact 1 tbsp = 3 tsp identity from Table B.6. Independence: primary. Access: open.
4. [4]King Arthur Baking Company. Ingredient Weight Chart, current revision; retrieved 30 July 2026. Cited as an independent publisher confirming the stick identity set this page is built on: "Butter — 8 tablespoons (1/2 cup): 4 ounces / 113 grams", which ties the stick, the eight tablespoons, the half cup and the four ounces together in one published line, with the gram figure rounded to 113 exactly as USDA's portion table has it. Independence: primary. Access: open.