How Many Grams Are in an Ounce?

This is a weight conversion, so it is the same number whether you are weighing flour, coffee, cheese or anything else. The precise factor is 1 ounce equals 28.349523 grams, which almost everyone shortens to 28.35 g. In the other direction, 1 gram is about 0.0353 ounces, so it takes a little more than 28 grams to make a single ounce.

That single number unlocks every other ounce and gram conversion you are likely to need. Once you know one ounce is roughly 28 grams, you can scale up to pounds, kilograms and recipe quantities in your head. The rest of this guide explains where the figure comes from, when to use the exact version, and how to avoid the mistakes that trip people up.

Where the 28.35 figure comes from

The ounce most people mean is the avoirdupois ounce, the everyday unit used for groceries, body weight and postage in the United States and, informally, in the United Kingdom. By international agreement, one avoirdupois pound is defined as exactly 453.59237 grams. A pound contains 16 ounces, so dividing 453.59237 by 16 gives 28.349523 grams per ounce. That is the source of the number, and it is fixed by definition rather than measured.

Because the value is exact, you can trust it for science, shipping and trade. In practice the level of precision you keep depends on the job. A postal worker weighing a parcel and a baker measuring chocolate do not need six decimal places. Rounding to 28.35 g is accurate enough for almost every kitchen and shipping task, and rounding further to 28 g is fine for quick estimates.

Exact vs rounded: which should you use?

Choosing between the exact and rounded values is mostly about how the small difference adds up. One ounce rounded to 28 g loses about 0.35 g, which is invisible for a single item but grows when you multiply.

• Use 28 g for fast mental maths, shopping estimates and rough recipe scaling where a gram or two does not matter.
• Use 28.35 g for everyday cooking, baking and parcel weights, where it is precise enough yet easy to remember.
• Use 28.349523 g for laboratory work, precious metals or anything where the total spans many ounces and errors compound.
• When converting large amounts, do the full-precision maths first and round only the final answer.

Ounce to gram chart

This chart covers the conversions that come up most often in kitchens and at the post office. The exact column uses 28.349523 g per ounce, while the rounded column gives a clean number for quick reference.

US, UK and metric differences

The avoirdupois ounce is the same 28.35 g in both the United States and the United Kingdom, so a recipe that calls for ounces of butter works identically on either side of the Atlantic. The metric world uses grams and kilograms instead, and 1 kilogram equals 1000 grams or about 35.27 ounces. Most modern British recipes are written in grams, while many US recipes still use ounces and cups, which is why a reliable converter is so handy.

One source of genuine confusion is the troy ounce, used only for precious metals such as gold and silver. A troy ounce is heavier, at about 31.10 grams, so a troy ounce of gold weighs more than a normal ounce of sugar. Unless you are dealing with bullion or jewellery, you want the avoirdupois ounce of 28.35 g. If you also juggle volume measures, the guide on ounces in a cup explains how the word ounce changes meaning between weight and volume.

Practical kitchen and real-world examples

Seeing the conversion attached to familiar items makes it stick. Here are quantities you have probably handled, expressed both ways.

• A standard US chocolate bar is often 1.55 oz, which is about 44 grams.
• A quarter-pound burger patty is 4 oz, or roughly 113 grams of meat.
• A typical bag of coffee is 12 oz, equal to about 340 grams of beans.
• A stick of US butter is 4 oz, which is 113 grams and equals half a cup.
• A letter that costs standard postage usually weighs under 1 oz, or under 28 grams.

When you are scaling a recipe, multiplying ounces by 28.35 keeps the proportions correct even if you switch the whole recipe to grams. If your measuring also involves spoons and cups, the breakdown in teaspoons in a tablespoon pairs nicely with this weight guide for fully metric cooking.

Common mistakes to avoid

Most ounce to gram errors come from mixing up units that share a name or rounding at the wrong moment. Watch for these traps.

• Confusing a fluid ounce with a weight ounce. A fluid ounce measures volume, not weight, so it does not convert directly to grams.
• Using the troy ounce by accident. Stick to 28.35 g for food and 31.10 g only for precious metals.
• Rounding too early in a multi-step calculation, which lets small errors stack up into a noticeable difference.
• Assuming grams of one ingredient equal grams of another by volume. Weight is weight, but a cup of flour and a cup of water weigh different amounts.
• Forgetting that 16 ounces make a pound, not 100, when converting larger weights.

Convert any weight instantly

When you need grams to pounds, kilograms to ounces, or anything in between, type the number into the weight converter and read the answer. It handles the exact factors for you, so there is no rounding to remember and no risk of grabbing the troy ounce by mistake.