How Many Grams in an Ounce? Conversion Guide & Charts
You’ve probably stood in the kitchen, recipe in hand, wondering how many grams are in that ounce measurement—the answer isn’t as straightforward as it seems because there are two different ounce systems. This guide lays out both conversions with exact numbers, clear tables, and the why behind each system.
1 standard ounce: 28.35 g ·
1 troy ounce (gold): 31.1035 g ·
1 pound: 453.592 g ·
1/2 ounce: 14.175 g ·
1/4 ounce: 7.0875 g ·
1/8 ounce: 3.54375 g
“The grain is a legally defined unit within the imperial and US customary systems, fixed at 64.79891 milligrams by the 1959 agreement.”
Quick snapshot
- 1 standard ounce = 28.3495 grams (Wikipedia – Avoirdupois system)
- 1 troy ounce = 31.1034768 grams (Wikipedia – Troy weight)
- Consumer recipes often round 1 oz to 28 g, which can shift small-batch results
- The abbreviation for troy ounces can appear as ‘oz t’ or ‘ozt’ and usage varies
- The exact historical origin of the troy ounce from Troyes, France is not definitively proven
- International yard & pound agreement (1959-07-01) fixed the grain at 64.79891 mg (Wikipedia – Troy weight)
- Use the tables below to convert any ounce value instantly for cooking, gold, or shipping
Six common conversions, one key observation: the troy ounce is about 9.7% heavier than the standard ounce, a difference that matters when you’re weighing precious metals.
| Unit | Grams (exact) | Common rounding |
|---|---|---|
| 1 standard ounce (oz) | 28.349523125 | 28.35 g |
| 1 troy ounce (ozt) | 31.1034768 | 31.10 g |
| 1 pound (lb) | 453.59237 | 453.6 g |
| 1/2 ounce | 14.1747615625 | 14.175 g |
| 1/4 ounce | 7.08738078125 | 7.0875 g |
| 1/8 ounce | 3.543690390625 | 3.54375 g |
How many grams are in an ounce?
What is the standard ounce to grams formula?
- Formula: grams = ounces × 28.349523125 (exact) or × 28.35 (rounded)
- A standard (avoirdupois) ounce contains 437.5 grains (Wikipedia – Avoirdupois system)
- One grain equals exactly 64.79891 milligrams per the 1959 agreement (NIST – Weights and Measures)
The avoirdupois system, used for food and everyday goods in the United States, defines the ounce you see on cereal boxes and produce scales (Britannica – Avoirdupois system).
Why does the conversion matter for recipes?
- Many US recipes list dry ingredients in ounces, while digital scales read grams
- Rounding to 28 g per ounce can lead to small errors in baking (e.g. 1% less flour per ounce)
- For precision, use the exact factor 28.35 g
The implication: one conversion factor fits everyday needs, but the difference between 28 and 28.35 grams adds up when you scale a recipe to multiple cups.
How many grams in an ounce of gold?
What is a troy ounce?
“The troy ounce derives from the market town of Troyes, France, and was historically used for precious metals in medieval Europe.”
- A troy ounce equals 31.1034768 grams exactly (Wikipedia – Troy weight)
- One troy ounce contains 480 grains, and there are 12 troy ounces in a troy pound
- The system traces back to the market town of Troyes, France (Britannica – Troy weight)
Gold, silver, platinum, and palladium are all traded in troy ounces on global markets (StoneX – Financial glossary: troy ounce). The United States Mint uses troy ounces for its bullion coin specifications (U.S. Mint – Coin specifications).
How does a troy ounce differ from a standard ounce?
- A troy ounce is about 9.7% heavier than an avoirdupois ounce (Wikipedia – Troy weight)
- 1 troy ounce = 1.0971 avoirdupois ounces; conversely, 1 avoirdupois ounce = 0.9115 troy ounces (Metric Conversions)
- Abbreviation for troy ounce is “oz t” or “ozt”; standard ounce is just “oz” (Britannica – Avoirdupois system)
If you buy a 1‑oz gold bar, you’re getting 31.1 grams of gold — not 28.35. That extra 2.75 grams per ounce explains why gold prices seem higher per ounce than you’d expect from grocery-store logic.
The pattern: precious metals use a heavier ounce because the troy system was designed for high-value, low-weight trade where every grain mattered.
How many grams in a half ounce, quarter ounce, and 1/8 ounce?
Half ounce to grams
- 1/2 ounce = 14.175 grams (rounded from 14.17476)
- Commonly used for spice jars and gold fractional rounds
Quarter ounce to grams
- 1/4 ounce = 7.0875 grams (exact 7.08738)
- Often seen in cannabis and gold coin denominations
1/8 ounce to grams
- 1/8 ounce = 3.54375 grams (exact 3.54369)
- Frequent measure for culinary herbs and small bullion pieces
All fractional conversions derived by dividing the exact ounce value: divide 28.349523125 by 2, 4, or 8.
Why this matters: fractional conversions are essential for portion control in recipes, investment buying, and shipping cost calculations.
How many grams are in a pound?
Converting pounds to grams
- 1 pound = 453.592 grams (exactly 453.59237) (Wikipedia – Avoirdupois system)
- Derived from 16 avoirdupois ounces × 28.349523125 g
How many ounces in a pound?
- 1 pound = 16 standard ounces
- 1 troy pound = 12 troy ounces (used only in bullion pricing)
The avoirdupois pound (453.6 g) and the troy pound (373.2 g) are very different. A gold bar that weighs one troy pound would contain only 12 troy ounces — but weigh 31.1035 × 12 = 373.2 grams, not 453.6. Confusing the two could cost you.
The trade-off: if you’re converting pounds to grams for shipping, the avoirdupois pound is standard. But for precious metals, the troy pound is historical; today gold is quoted per troy ounce, not per pound.
Comparison: standard ounce vs. troy ounce
Two ounces, two weights, one key difference demonstrated in the table below.
| Property | Standard ounce (avoirdupois) | Troy ounce |
|---|---|---|
| Grams (exact) | 28.349523125 | 31.1034768 |
| Grains | 437.5 | 480 |
| Used for | Food, water, milk, salt, everyday goods | Gold, silver, platinum, palladium |
| Ounces per pound | 16 | 12 |
| Legal status (US) | Customary unit (NIST – Weights and Measures) | Recognized for precious metals (NIST – Weights and Measures) |
| Rounded value | 28.35 g | 31.10 g |
The pattern: the troy ounce is about 10% heavier, and this difference compounds when trading at hundreds of dollars per ounce.
How to convert ounces to grams in three steps
- Identify the ounce type. If it’s food, drugs, or general weight, it’s an avoirdupois ounce. If it’s gold, silver, or other bullion, it’s a troy ounce.
- Multiply by the correct factor. Standard: × 28.35. Troy: × 31.10 (use exact decimals for precision).
- Round appropriately. For cooking, 1 decimal place is enough. For bullion, keep 2–4 decimals for trade calculations.
Example: 3 ounces of gold = 3 × 31.1035 = 93.3105 grams. 8 ounces of flour = 8 × 28.35 = 226.8 grams.
The key is to always identify the ounce type first; the rest is simple arithmetic.
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For a more detailed breakdown of the differences between avoirdupois and troy ounces, see this detailed avoirdupois vs troy guide.
Frequently asked questions
Does 30 grams equal 1 ounce?
No. 30 grams is about 1.058 standard ounces — close but not exact. One standard ounce is 28.35 grams.
Is 28 grams equal to 1 ounce?
Only as a rough approximation. The exact value is 28.3495 grams. Many recipes round to 28 g, but for precision use 28.35.
What is the difference between a troy ounce and a standard ounce?
A troy ounce is heavier — 31.1035 g vs. 28.3495 g — and is used exclusively for precious metals.
How much is 1 gram of gold worth in money?
The value changes daily with the spot price. At a spot price of, say, $2,000 per troy ounce, 1 gram would be worth about $64.30 (2000 / 31.1035). Check the live gold price for today’s rate.
Why do recipes use 28 grams instead of 28.35 grams?
Convenience. The difference (0.35 g per ounce) is negligible in most recipes, but for scaling large batches it’s better to use the full decimal.
These answers cover the most common points of confusion.
For anyone measuring ingredients, mailing packages, or investing in gold, the ounce is not one thing — it’s two. The avoirdupois ounce (28.35 g) rules everyday life, while the troy ounce (31.10 g) governs precious metals. Confusing them can shortchange a baker by 9.7% or misprice a bullion trade. For Australian and international readers, the rule is simple: if it’s edible, use 28.35; if it’s shiny and traded, use 31.10. Get the system right, and the grams follow.
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