Weight Loss & Fitness

1 oz to Grams: What One Ounce Equals

Convert 1 oz to grams: one ounce equals 28.35 g. Learn the exact avoirdupois factor, how it is used in cooking and shipping, and common ounce-to-gram values.

Why One Ounce Matters

The ounce is the small-weight unit in US recipes, postal rates, and jewelry, while grams are the metric default. Converting an ounce to grams is one of the most repeated kitchen and shipping calculations.

One avoirdupois ounce equals 28.349523125 g. Our oz to grams converter returns it precisely; the rounded 28.35 g is what you usually see.

The 1 oz to Grams Formula

The avoirdupois ounce is defined as exactly 28.349523125 grams (one sixteenth of a pound). Multiply ounces by 28.349523125 to get grams.

The Exact Calculation

For 1 oz: 1 × 28.349523125 = 28.349523125 g, rounded to 28.35 g. For 2 oz: 2 × 28.3495 = 56.70 g. The factor is exact, set by the pound definition.

Note the troy ounce used for precious metals is different (31.1035 g). For food, postage, and everyday weight, the avoirdupois ounce above is the right one.

Why 28.35 Grams

The ounce comes from the pound, defined as 0.45359237 kg. Divide that by 16 (ounces per pound) and you get 0.028349523125 kg, or 28.349523125 g per ounce. That is the source of the 28.35 figure.

What 28.35 g Looks Like

Twenty-eight grams is a modest kitchen amount: about two tablespoons of flour, a slice of bread, or a small handful of nuts. On a postal scale, 1 oz is the typical minimum step for first-class letters.

Compare with nearby values: 0.5 oz = 14.17 g, 2 oz = 56.70 g, 4 oz = 113.40 g (a common serving size, a quarter pound).

1 oz Compared With Nearby Weights

For reference, 1 oz = 28.35 g and 1 g = 0.035274 oz. Each extra ounce adds 28.35 g, so 8 oz (half a pound) is 226.8 g.

For the reverse direction, our guide to grams to ounces shows how metric recipe amounts map back to ounces.

When You Need oz in Grams

The conversion is essential in cooking and baking, where US recipes list ounces and metric scales show grams. It also appears in shipping, where carriers price by ounce or gram and you must match the unit.

It helps when following a recipe written in the other system, since a small error in a baking ratio matters more than in a stew.

Frequently Asked Questions

How many grams is 1 oz?

1 avoirdupois ounce equals 28.349523125 g, normally rounded to 28.35 g.

How do I convert oz to grams?

Multiply ounces by 28.349523125. For 2 oz: 2 × 28.3495 = 56.70 g.

Is a troy ounce the same?

No. A troy ounce (precious metals) is 31.1035 g; the everyday avoirdupois ounce is 28.35 g.

How many grams is 4 oz?

4 oz equals 113.40 g, a common quarter-pound serving size.

How many oz is 100 grams?

100 g equals about 3.527 oz (100 / 28.3495).

Try the Calculator

oz to Grams Converter

Get instant, accurate results with our free converter.

Use Converter →

Quick Summary

1 oz equals 28.35 g. Multiply ounces by 28.349523125 (the exact grams per avoirdupois ounce): 1 × 28.3495 = 28.35 g. Note the troy ounce for metals is 31.10 g.

Related Guide

Grams to Ounces: Convert Grams to Ounces for Cooking and Packaging

Convert grams to ounces with the exact 0.035274 factor. Translate metric recipe weights, portions, and packaging values into US ounces.

Read Full Guide →

Convert Another Unit

lbs → kg lbs → kg lbs → kg lbs → kg °F → °C °F → °C °F → °C ft → m

Disclaimer

Unit conversions on this site use internationally recognized, fixed conversion factors (for example, 1 inch = 2.54 cm, 1 pound = 0.45359237 kg, 1 °F = (°C × 9/5) + 32). They are provided for general, informational, and educational use. For applications where accuracy is critical — such as medical dosing, engineering, scientific research, trade, or legal compliance — always verify results against authoritative sources such as the U.S. National Institute of Standards and Technology (NIST) and the official International System of Units (SI) brochure, and follow any applicable local standards.

Exact Constants & Authoritative Sources

Every conversion on this page uses the fixed, internationally agreed constants below — drawn from NIST and the SI Brochure. No values are estimated or rounded as if exact. See the full list on our Sources & Standards page.

EXACT1 pound (lb, avoirdupois) = 0.45359237 kilograms (exact)
EXACT1 ounce (oz, avoirdupois) = 28.349523125 grams (exact, 1/16 lb)
EXACT1 stone (st) = 6.35029318 kilograms (exact, 14 lb)
EXACT1 short ton (US) = 907.18474 kilograms (exact, 2000 lb)

Common Pitfalls & How to Avoid Them

Mass vs. weight

The pound and kilogram are units of MASS, not force. On Earth, mass and "weight" read the same number in practice, but a 70 kg mass weighs less on the Moon. UnitFig converts mass; for scientific force you need newtons (1 lbf = 4.4482216152605 N, exact).

Avoirdupois vs. troy ounce

Cooking and body weight use the avoirdupois ounce (28.349523125 g). Gold and precious metals use the troy ounce (31.1034768 g). Never mix them — the error is about 10%.

Rounding the factor

Using 2.2 instead of the exact 2.20462262 overstates small errors at large values. For medical dosing or competition weight classes, keep the full factor or use a converter.

A unit-conversion reference site has no manufacturer-specific or device calibration parameters, so "layered tuning" does not apply here. The only real error-handling is input validation: the converter rejects non-numeric, empty, or out-of-range entries and shows a clear message, then falls back to exact constants above. No estimated or rounded figures are ever presented as exact.

Authoritative sources for this page

NIST (U.S. National Institute of Standards and Technology) — NIST SP 330 — The International System of Units (SI), 2019 edition

Last Updated 2026 | This article was reviewed for accuracy