Ounces to grams

The reverse case shows up when a US recipe listing ingredients in ounces is cooked on a metric kitchen scale, or when a US-labeled product's net weight needs converting to compare against a metric-labeled equivalent on the same store shelf. Postage and shipping forms are a second common trigger, since many carriers price by the gram once a package crosses a border, and a letter or small parcel weighed in ounces at home needs a gram figure before it can be entered on an international customs or postage form. Jewelry and precious-metal listings add a third: a small item weighed on a US postal scale in ounces is often described online in grams, so a buyer comparing two listings needs both figures to line up.

Home crafters run into the same conversion from the other direction: soap making, candle pouring, and coffee roasting recipes are usually written in grams for precision, but many US kitchen scales default to ounces unless switched. A protein supplement scoop or nutrition-label serving size given in grams is another spot where knowing the ounce equivalent helps compare it against a US recipe or dosage that still uses ounces, and it also helps a shopper work out whether a smaller metric-labeled package is actually cheaper per ounce than a larger US one.

An avoirdupois ounce, the everyday US weight ounce, converts to grams with a single fixed multiplier, since both units sit on the same linear mass scale with no offset to worry about.

Multiply the ounce value by 28.349523125 to get grams:

g = oz × 28.349523125

At small values this is easy to check by hand: 1 oz is 28.3495 g, 4 oz comes to 113.398 g, and 16 oz, a full pound, works out to exactly 453.59237 g, since a pound and 16 ounces describe the same weight.

For everyday cooking or shipping, rounding to one decimal place (28.3 g per ounce) is plenty accurate; lab, jewelry, or dosage work should keep the full 28.3495 g figure, since the rounding error compounds once several ounces are added together, and a scale's own display precision often matters more than the conversion factor itself at that point.

The most common slip is mixing up this weight ounce with the fluid ounce, a volume unit with a different, unrelated conversion figure. A recipe calling for 8 oz of flour (a weight) and 8 fl oz of milk (a volume) are not interchangeable, even though both are written with the same oz abbreviation, and treating them as the same quantity will throw off a recipe's ratios noticeably.