How Much Is an Ounce? Grams, ML, & Gold Value Guide

Few numbers cause as much everyday confusion as the humble ounce because it can be a unit of weight, a measure of liquid, or the standard for pricing gold, depending on the context. Getting it wrong can throw off a recipe, a parcel, or even an investment.

1 avoirdupois ounce = 28.35 grams ·
1 troy ounce = 31.10 grams ·
1 US fluid ounce = 29.57 ml ·
1 UK fluid ounce = 28.41 ml ·
1 troy ounce of gold (as of page date) = $4,039.16

Five different ounce definitions, five different numbers. The table below shows the exact values you need for each context.

How many grams is 1 ounce?

What is the difference between avoirdupois and troy ounces?

• Avoirdupois ounce: 1 oz = 28.3495 grams (commonly 28.35 g). Used for most everyday items: food, postal packages, body weight. (Britannica encyclopedia entry)
• Troy ounce: 1 troy oz = 31.1035 grams (commonly 31.10 g). Used exclusively for precious metals like gold, silver, and platinum. (BullionVault precious metals guide)

The catch: If you’re measuring something from the grocery store, you want the lighter avoirdupois ounce. If you’re weighing gold, you want the heavier troy ounce. Using the wrong system could cost you nearly 10% in weight — a costly mistake if you’re valuing bullion.

Is 1 oz 28 or 31 grams?

Which ounce is used for precious metals?

• 28 g is close to the avoirdupois ounce (28.35 g). This is the correct answer for everyday weight.
• 31 g is close to the troy ounce (31.10 g). This is the answer for gold, silver, and other precious metals.

“Is 30 grams the same as 1 ounce?” Only if you’re using the US food‑labelling fluid ounce, which is defined as exactly 30 ml (Wikipedia reference). For mass, 30 g is about 5.8% too heavy for an avoirdupois ounce and about 3.5% too light for a troy ounce — so no, it’s not the same.

The implication: always verify which ounce system is being used to avoid costly mistakes.

What does 1 oz look like?

Common visual references for one ounce

• A slice of bread weighs about 1 avoirdupois ounce.
• A golf ball weighs approximately 1.6 ounces, so a bit more than 1 oz.
• A standard shot glass holds 1.5 US fluid ounces — a useful visual for liquid volume.
• One troy ounce of gold is a coin about the diameter of a US quarter but thicker, or a small bar the size of a credit card.

The implication: for weight, think of a small handful of everyday objects. For gold, the physical size is surprisingly compact — $4,039 worth of gold fits in your palm.

How much is an ounce to ml?

US fluid ounce vs UK fluid ounce

• US fluid ounce: 1 fl oz = 29.57 ml (Britannica conversion)
• UK fluid ounce (Imperial): 1 UK fl oz = 28.41 ml (Britannica)

A recipe from the UK using a pint (20 fl oz) will yield a different volume than one from the US using a pint (16 fl oz). The trade-off: if the cookbook doesn’t specify, assume 30 ml per fluid ounce — the US food‑labelling standard — but check the origin. (Wikipedia food‑labelling definition)

How much is an ounce of gold?

How is gold priced per ounce?

Gold is traded in troy ounces (31.10 g). The spot price fluctuates constantly. As of this writing, one troy ounce of gold is quoted at $4,039.16 on GoldAvenue (live precious‑metals pricing). This price is for 999.9 fine gold; lower purities cost less.

The trade-off: you never pay exactly the spot price. Dealers add a premium (often 1–5%) for coins and bars, and you’ll lose a spread when selling. Always use a live price feed for current values. (GoldPrice.org live chart)

The pattern: the gold market relies on troy ounces, and any deviation from that standard can lead to significant financial errors.

“The international avoirdupois ounce was defined by the 1959 yard and pound agreement as exactly 0.45359237/16 kilograms.”

Wikipedia (reference on ounce definitions)

“Gold is commonly quoted per troy ounce in bullion markets, and the standard conversion is 31.1034768 grams per troy ounce.”

GoldPrice.org (live pricing authority)

“One troy ounce equals 31.1034768 grams, providing a gold‑market‑specific conversion reference.”

BullionVault (precious‑metals education)

“The avoirdupois ounce is the everyday mass ounce used in common commerce, while the fluid ounce is a unit of volume, not mass.”

Britannica (encyclopedia reference)

For anyone reading a recipe, weighing a package, or buying gold, the choice between ounce types isn’t a detail — it’s a decision with real consequences. Use the wrong ounce and you could overpay, over‑serve, or under‑ship. The fix is simple: ask which ounce the source means, then reach for the conversion table above.

Frequently asked questions