Ounces to Grams Converter (avdp weight)

The Ounces to Grams Converter translates any weight between avoirdupois ounces (oz), grams (g), kilograms (kg), milligrams (mg), pounds (lb), and troy ounces (oz t) using the exact 28.349523125 g/oz factor published in NIST Special Publication 811 and fixed by the 1959 international yard and pound agreement. Type a value into the ounces or grams field and every other unit updates instantly, so you can read the same mass in any system without doing the arithmetic by hand. The converter is useful for home cooks adapting European recipes that quote ingredient quantities in grams, bakers scaling US recipes that use ounce-based butter sticks, parents weighing baby food or infant formula where gram accuracy matters, postal and shipping clerks quoting parcel weights to international carriers, jewellers and gold dealers comparing troy and avoirdupois units, students doing unit-conversion problems in physics or chemistry labs, and anyone who has ever wondered whether an "8 oz steak" weighs 226 grams or 240 grams. The conversion is exact by international definition: every figure on this page traces back to the 1959 yard and pound agreement with no intermediate rounding.

How to Use the Ounces to Grams Converter

1. Type a number into the Ounces (oz) field on the left to see the equivalent mass in grams, kilograms, milligrams, pounds, and troy ounces on the right.
2. Type a number into the Grams (g) field to see the equivalent in ounces on the left and every other unit on the right.
3. For the Ounces to Grams Converter (avdp weight), The two fields stay in sync as you type, editing one updates the other automatically.
4. Read the result box for every common unit side by side: ounces, grams, kilograms, milligrams, pounds, and troy ounces.
5. Use the Copy grams or Copy ounces buttons to copy the headline value to the clipboard for pasting into a recipe card, shipping label, or calculator.
6. Open the About avoirdupois vs troy ounces vs fluid ounces panel at the bottom to read the distinctions between the three different "ounces" in common use.

The Conversion Formula

The conversion between ounces and grams sits on one international definition:

Ounces to grams: grams = ounces × 28.349523125

Grams to ounces: ounces = grams ÷ 28.349523125

The constant 28.349523125 g/oz is exact, not approximate. The kilogram was redefined in 2019 by fixing the Planck constant, but the practical relationship between the pound and the kilogram, and therefore the ounce and the gram, has been locked at the 1959 yard and pound values for every measurement made in commerce, science, and trade since then. A US kitchen scale reading in grams, a German postal scale, and an Australian parcel scale all give the same answer to within the resolution of the instrument when measuring the same object.

The same constant gives all the bonus read-outs directly:

• Kilograms: kg = oz × 28.349523125 / 1000
• Milligrams: mg = oz × 28.349523125 × 1000
• Pounds: lb = oz / 16 (since 1 lb = 16 oz exactly)
• Troy ounces: oz t = oz × 28.349523125 / 31.1034768 (a different unit, included for precious-metals work)

Because every step uses exact constants, the conversion carries no rounding beyond the four-to-six-decimal display. The reverse direction (grams → ounces) uses simple division by the same constant, so the result is just as exact.

Why the Avoirdupois Ounce Is Exactly 28.349523125 Grams

Before 1959, the pound was defined as exactly 0.453592338 kilograms in some countries and 0.45359265 kilograms in others, with corresponding ounces drifting by about 0.07 grams per ounce. The 1959 international yard and pound agreement fixed the pound at exactly 0.45359237 kilograms, ratified by the United States, the United Kingdom, Canada, Australia, New Zealand, South Africa, and other Commonwealth countries. Because the pound is divided into 16 avoirdupois ounces by definition, the ounce becomes exactly 0.45359237 / 16 kilograms = 0.028349523125 kg = 28.349523125 g. NIST Special Publication 811 publishes the exact factor and BIPM references it in the SI Brochure. The 2019 redefinition of the kilogram did not change this relationship, the pound-to-kilogram ratio is still 0.45359237 exactly.

Worked Examples

Example 1, One ounce (the basic case). 1 oz × 28.349523125 g/oz = 28.349523125 g. So 1 ounce weighs exactly 28.349523125 grams, useful as a sanity check and the canonical shortcut to remember.

Example 2, Four ounces (a US stick of butter). 4 oz × 28.349523125 g/oz = 113.3980925 g. US butter is sold in 1-pound packages containing four sticks, each marked as 4 oz (113 g) on the wrapper.

Example 3, Eight ounces (a US cup of water). 8 oz × 28.349523125 g/oz = 226.796185 g. An 8 oz cup of water is the standard US liquid measure; in grams it weighs 226.8 g (less than a metric 250 mL cup at 250 g).

Example 4, Sixteen ounces (one pound). 16 oz × 28.349523125 g/oz = 453.59237 g exactly. This is the defining relationship: 1 pound = 16 ounces = 453.59237 grams. The calculator shows 16 oz → 453.59237 g → 1 lb exactly.

Example 5, One kilogram (reverse direction). 1000 g ÷ 28.349523125 g/oz = 35.27396194 oz. One kilogram equals about 35.27 ounces or 2.20462 pounds. A 1 kg bag of flour is about 2.2 lb.

Example 6, A 16-ounce steak. 16 oz × 28.349523125 g/oz = 453.59237 g, exactly one pound. The customer who wants the metric weight reads 453.6 g on the calculator.

Example 7, A 100-gram bar of chocolate. 100 g ÷ 28.349523125 g/oz = 3.52739619 oz = 0.22046 lb. The calculator shows all three at once.

Example 8, A 5-pound bag of flour. 5 lb × 453.59237 g/lb = 2267.96185 g = 2.26796 kg = 80 oz. The same bag is 80 ounces (5 × 16) or 2.27 kilograms, and the converter reads all three.

Where the Conversion Shows Up

• Cooking and baking: American recipes call for ingredients in ounces and cups; European recipes call for grams. The converter lets you translate either way, and a kitchen scale set to grams is the most reliable way to bake European bread in a US kitchen.
• Recipe scaling: When a recipe is doubled or halved, the ounces-to-grams ratio is preserved, so the converter gives the same answer per ounce regardless of batch size.
• Postal and shipping: USPS, Royal Mail, Canada Post, and most international couriers quote parcel weights in both ounces (small packages) and pounds (heavier parcels), and customs forms require kilograms. The converter bridges all three systems.
• Jewellery and precious metals: Gold, silver, platinum, and palladium are weighed in troy ounces (31.1034768 g exactly), not avoirdupois ounces. The bonus row lets a jeweller read a mass in either system.
• Science and laboratory work: US lab balances read in grams, while reagent data sheets and pharmaceutical references quote masses in ounces or pounds.
• Nutrition and dietary tracking: FDA nutrition labels list serving sizes in grams, but food packaging often quotes ounces. The converter translates between them.
• Education: Teaching the relationship between SI mass units (kilogram, gram, milligram) and US customary mass units (pound, ounce) requires an exact conversion, the same NIST factor that appears in standard physics and chemistry textbooks.

Common Mistakes

• Confusing weight ounces with fluid ounces. A fluid ounce (fl oz) is a unit of volume, exactly 29.5735295625 mL for the US fluid ounce, not a unit of weight. A fluid ounce of water weighs about one avoirdupois ounce, but a fluid ounce of honey weighs about 1.4 oz because honey is denser. Always check whether a recipe or product label means weight (oz) or volume (fl oz) before converting.
• Using the troy ounce by accident. The troy ounce (31.1034768 g exactly) is used for precious metals and is about 9.7 percent heavier than the avoirdupois ounce. A gold dealer quoting "1 oz" means a troy ounce; a butcher quoting "1 oz" means an avoirdupois ounce. The calculator shows both so you can read the right one.
• Mixing up ounces and pounds in the input. 1 pound equals 16 ounces. If a recipe says "1 lb of beef" and you type "1" into the ounces field, you will get 28.35 g, about 0.06 lb, instead of the intended 453.6 g. Type the ounces value carefully, or use the kilograms/pounds read-outs as a sanity check.
• Forgetting that a US stick of butter is 4 oz, not 8 oz. US butter wrappers are printed "4 oz (113 g)" per stick. Recipes calling for "1 stick of butter" mean 4 oz / 113 g, not half a pound. The converter lets you check: 4 oz → 113.4 g, 8 oz → 226.8 g, 16 oz → 453.6 g.
• Rounding too early in a chain of conversions. If you need to convert 5 oz to kilograms and back, do it in one step (5 × 28.349523125 / 1000 = 0.14175 kg) rather than rounding the intermediate value (5 × 28.35 = 141.75 g, then 141.75 / 1000 = 0.14175 kg, close but not exact). The calculator carries full precision until display.

Quick Mental Conversion Trick

For a rough estimate, 1 oz ≈ 28 g (within 1 percent of the exact 28.35 g), close enough for most cooking, baking, and shipping estimates. A 4-oz stick of butter ≈ 113 g is the canonical US baking shortcut. A 1-pound package ≈ 454 g matches the exact 453.59 g closely enough for everyday use. In reverse, 100 g ≈ 3.5 oz, 500 g ≈ 17.6 oz, and 1 kg ≈ 35 oz (or 2.2 lb). For postal and shipping work, use the exact value to avoid rounding-error disputes.

When to Use a Different Tool

This converter is precise enough for cooking, baking, postal use, and most shipping work. For pharmaceutical compounding, laboratory chemistry, or any legally regulated application, use a calibrated balance traceable to national standards (NIST in the US, NPL in the UK) rather than relying on a calculator. For commercial gold or silver transactions, use a troy-ounce-only scale. For very large masses, switch to kilograms or metric tons directly rather than converting through ounces.

Frequently Asked Questions

How many grams are in one ounce? One avoirdupois ounce equals exactly 28.349523125 grams. This is fixed by the 1959 international yard and pound agreement and published in NIST Special Publication 811. Reverse: one gram equals 0.03527396 ounces.

How many ounces are in one pound? Sixteen avoirdupois ounces equal exactly one pound, and one pound equals exactly 453.59237 grams. So 1 lb = 16 oz = 453.59237 g, all exact.

How many grams are in one kilogram? One kilogram equals exactly 1000 grams, 35.27396 ounces, or 2.20462 pounds. Use this when reading metric recipes in ounces.

What is the difference between an avoirdupois ounce and a troy ounce? The avoirdupois ounce (1 oz = 28.349523125 g exactly) is the kitchen and postal unit. The troy ounce (1 oz t = 31.1034768 g exactly) is the precious-metals unit and is about 9.7 percent heavier. Use the right one for the right job.

Is a fluid ounce the same as a weight ounce? No. A US fluid ounce (fl oz) is a unit of volume, exactly 29.5735295625 mL, not a unit of weight. A fluid ounce of water weighs about one avoirdupois ounce, but a fluid ounce of honey weighs about 1.4 oz because honey is denser.

How accurate is the 28.349523125 g/oz factor? Exact by international definition, with no rounding. The 1959 yard and pound agreement fixed the pound at exactly 0.45359237 kilograms, and dividing by 16 (ounces per pound) and 1000 (grams per kilogram) gives 28.349523125 g/oz exactly.

can the Ounces to Grams Converter (avdp weight) be used for professional or commercial purposes? Yes, for recipe development, food labelling, postal quoting, and shipping estimates. For pharmaceutical compounding, laboratory chemistry, precious-metals trading, or any legally regulated transaction, use a calibrated balance traceable to national standards and verify with a domain expert.

How do I convert ounces to kilograms or milligrams? Divide grams by 1000 to get kilograms; multiply grams by 1000 to get milligrams. So 8 oz = 226.796 g = 0.226796 kg = 226,796 mg exactly. The calculator shows all four at once.

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References

• NIST Special Publication 811, Guide for the Use of the SI Units, publishes the exact 28.349523125 g/oz factor.
• 1959 international yard and pound agreement, fixes the pound at exactly 0.45359237 kilograms, from which the 28.349523125 g/oz factor is derived.
• BIPM SI Brochure (9th edition), references the same yard-and-pound agreement.
• ASTM E617, Standard Specification for Laboratory Weights and Precision Mass Standards, defines the avoirdupois ounce and pound for laboratory use.
• US Code of Federal Regulations, 21 CFR 101.9, Nutrition Labelling of Food, references the same 1959 definitions.
• Encyclopedia Britannica, Avoirdupois weight, historical and modern definitions of the ounce and pound.