Convert Ounces to Grams
Translate ounces into grams for precise baking measurements, gram-based nutrition labels and metric postal weights.
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1 oz = 28.35 g
One ounce equals exactly 28.3495 grams. To convert ounces to grams, multiply the ounce value by 28.3495 — so 5 oz = 141.75 g and 8 oz = 226.80 g. This is the international avoirdupois ounce used in the US and UK for food, mail and everyday weights. It is not the same as the troy ounce (31.1035 g) used for precious metals, and not the same as a fluid ounce, which measures volume.
Quick reference: ounces to grams
| Ounces | Grams |
|---|---|
| 0.5 | 14.17 g |
| 1 | 28.35 g |
| 2 | 56.70 g |
| 3 | 85.05 g |
| 4 | 113.40 g |
| 5 | 141.75 g |
| 6 | 170.10 g |
| 8 | 226.80 g |
| 10 | 283.50 g |
| 12 | 340.19 g |
| 16 | 453.59 g (1 lb) |
| 24 | 680.39 g |
| 32 | 907.18 g (2 lb) |
Formula and worked examples: ounces to grams
Formula: grams = ounces × 28.3495 • A 4 oz stick of butter → 4 × 28.3495 = 113.40 g (which is why European recipes usually round it to 115 g). • A 13 oz letter for USPS First-Class → 13 × 28.3495 = 368.54 g, just under the 400 g Royal Mail large-letter tier. • A 6 oz chicken breast on a US nutrition label → 6 × 28.3495 = 170.10 g, useful when logging food in a metric app.
When and why people use ounces to grams
Bakers convert ounces to grams because grams are far more precise: a kitchen scale reads to 1 g, while a 1 oz measure has a resolution of about 28 g. Serious baking sources like King Arthur and Cook's Illustrated publish weights in grams for the same reason. Shipping is the other everyday case. USPS, UPS and Royal Mail all bill by weight, and most international carriers accept only kilograms and grams on the customs form. Converting the scale reading from ounces to grams avoids rounding disputes at the counter. Standards note: the avoirdupois ounce is legally defined as 1/16 of the international pound, which is exactly 0.45359237 kg. That makes one ounce exactly 28.349523125 g under the 1959 international yard and pound agreement adopted by NIST and the UK's National Physical Laboratory.
Common mistakes to watch for when converting ounces to grams
The three biggest mistakes are mixing up ounces with fluid ounces, avoirdupois with troy, and rounded conversions with exact ones. A US fluid ounce is a volume of about 29.5735 ml and only matches 28.35 g for water — for oil, flour or honey the number will be different. A troy ounce (31.1035 g) is roughly 10 percent heavier than a normal ounce and is used only for gold, silver and gunpowder. Finally, many packaging labels round 16 oz to 450 g instead of the correct 453.59 g; the 3.6 g gap adds up over a recipe.
Ounces to Grams FAQ
- How many grams is 8 oz?
- 8 oz equals 226.80 g — exactly half a pound. This is the reference figure behind the 227 g rounding you see on many US-to-metric food labels.
- Is 1 oz exactly 28 grams?
- No. One avoirdupois ounce is 28.3495 g, not 28. The 28-gram shortcut is close enough for a shopping list but drifts noticeably in baking or shipping where the extra 1.2 percent matters.
- How many grams is 4 oz of butter?
- 4 oz of butter is 113.40 g. US stick butter is sold in 4 oz sticks, which is why European recipes translate them as 113 g or 115 g.
- What's the difference between ounces and fluid ounces?
- Ounces measure weight; fluid ounces measure volume. One US fl oz is about 29.5735 ml, and only equals 28.35 g when you're weighing pure water. For flour, oil or honey the gram figure will be very different.
- Is a troy ounce the same as a regular ounce?
- No. A troy ounce is 31.1035 g, roughly 10 percent heavier than the everyday avoirdupois ounce. Troy ounces are used only for precious metals like gold and silver.
- How many grams in 16 oz?
- 16 oz equals 453.59 g, or one pound. Packaging that lists 16 oz as 450 g is rounded down and off by about 3.6 g.
- How do I convert ounces to grams without a calculator?
- Multiply by 28 for a rough estimate, then add roughly 1 gram for every 3 ounces. So 9 oz ≈ 9 × 28 + 3 = 255 g (actual: 255.15 g).
- Which is more accurate for baking, ounces or grams?
- Grams. A digital scale reads grams at 1 g resolution, so a 200 g flour measurement is far more repeatable than '7 oz', which could sit anywhere between 198 g and 227 g depending on how it was rounded.
- Is the ounce-to-gram conversion the same worldwide?
- Yes for the avoirdupois ounce. Since 1959 the US, UK, Canada, Australia and New Zealand have all defined the ounce as exactly 28.349523125 g.
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Sources: NIST Handbook 44, BIPM SI brochure, and the 1959 international yard and pound agreement (avoirdupois ounce = 28.349523125 g exactly).