Ounce Abbreviation: oz and fl oz

Abbreviation for ounces: singular and plural

Unit symbols in English do not change in the plural, and ounces follow the same rule.

• One ounce: 1 oz
• Many ounces: 8 oz, 16 oz, 0.5 oz
• Spacing: leave a gap after the number, as in 6 oz. In tight labels you may see 6oz, which is common but less tidy.
• Period: most labels and recipes write oz with no period. Some older cookbooks use oz., and it is still understood.

Keep the letters lowercase. OZ in capitals usually appears only on all capital packaging.

Why the ounce abbreviation uses a z

There is no z in ounce, which puzzles a lot of people. The short form comes from onza, an old Italian word for the unit. Writers borrowed that spelling for the short form, and it stuck even after English settled on ounce for the full word. The pound abbreviation, lb, has a similar story, since it comes from a Latin word rather than the English one. See the abbreviation for pounds for that one.

oz vs fl oz: weight and volume

An ounce can measure how heavy something is or how much space a liquid takes up. Labels use different letters for each.

Water is close to 1 ounce of weight per fluid ounce, but most foods are not. A cup of flour weighs far less than 8 oz, and a cup of honey weighs more. That is why serious bakers use a kitchen scale.

Ounces in recipes and kitchens

Recipes often mix both kinds. "8 oz cream cheese" means a weight, usually one standard block. "4 fl oz milk" means half a cup. When a recipe says only "oz" for a liquid, it usually means fluid ounces.

• 2 tablespoons = 1 fl oz
• 8 fl oz = 1 cup
• 16 fl oz = 1 pint
• 128 fl oz = 1 gallon

Related kitchen short forms have their own pages: tablespoon, cup and gram.

Troy ounces and UK ounces

Two less common ounces have their own rules.

• Troy ounce (ozt or oz t): used for gold, silver and other precious metals. It is heavier than a kitchen ounce, at about 31.1 grams.
• Imperial fluid ounce: used in the UK. It is slightly smaller than the US fluid ounce, about 28.4 milliliters, and 20 of them make an imperial pint.

If you follow a British recipe or buy metal coins, check which ounce is meant before you convert.

Examples of oz in everyday writing

Sample lines like these turn up on cards, labels and slips; for kitchen and shipping shorthand beyond ounces, try our common abbreviations pages.

• "Add 3 oz shredded cheese."
• "Each serving is 1.5 oz."
• "The letter weighs under 1 oz, so one stamp is enough."
• "Pour 6 fl oz warm water into the bottle."
• "The steak was about 10 oz before cooking."
• "Two 8 oz jars of salsa fit in the gift box."