1 oz to Grams Conversion: Standard vs Troy Ounce Guide

The number of grams in one ounce depends entirely on whether you are measuring a recipe or a bar of gold. A standard ounce equals 28.3495 grams, while a troy ounce used for precious metals weighs 31.1035 grams. This guide lays out the exact numbers for both everyday and precious-metals ounces, with practical examples for cooking and bullion.

1 standard ounce (oz): 28.3495 grams (g) ·
1 troy ounce (gold/silver): 31.1035 grams ·
1 oz of gold (troy): ≈ 31.1 g ·
1 oz of all-purpose flour: ≈ 28.35 g

The difference between a standard and troy ounce is about 10%, which matters for both baking and buying gold.

The implication: a troy ounce is about 9.7% heavier than a standard ounce, which matters when pricing precious metals or scaling recipes.

Is 1 oz 28 or 31 grams?

What is the exact conversion factor?

The avoirdupois ounce — the one used for food, postal packages, and most household items — is defined as exactly 28.349523125 grams according to NIST’s Handbook 44 Appendix C (the U.S. government’s official measurement document). For everyday purposes, rounding to 28.35 g is more than accurate enough.

Why do some sources say 28 g and others 31 g?

The 31 g figure comes from the troy ounce, a separate unit used almost exclusively for precious metals. NIST’s Precious Metals Conversion Information gives the exact weight as 31.1034768 g. Most gold dealers round to 31.10 g. So both numbers are correct — they just refer to different ounces.

What this means: always check whether “oz” means avoirdupois or troy. Cooking and grocery items are almost always the former; bullion, coins, and jewelry are almost always the latter.

How Many Grams In An Ounce Of Gold?

Troy ounce vs standard ounce for gold

Gold is weighed in troy ounces. The NIST precious-metals table states that 1 troy ounce equals 31.1034768 grams. A troy ounce is composed of 480 grains, while the standard ounce has 437.5 grains — making the troy version about 9.7% heavier, as noted by U.S. Money Reserve (bullion education specialist).

Does gold purity affect the weight conversion?

No. Gold’s karat tells you the purity (e.g., 24k is 99.9% pure), but it does not change the weight of the ounce. A 1 oz troy bar of 24k gold still weighs 31.1035 g — it just contains slightly less pure gold if the karat is lower. The conversion factor from troy ounce to grams is always the same.

How many grams in 24k gold per ounce?

Exactly 31.1034768 grams per troy ounce. Great American Coin Company (bullion dealer) notes that a 1 oz gold coin contains about 31.10 g of gold, using the standard industry rounding.

The pattern: gold investors should always use the troy conversion. The standard ounce conversion would undercount the metal weight by nearly 10%.

How many 1 oz is in 1 kg?

How many ounces make a kilogram?

One kilogram (1000 g) divided by 28.3495 gives you 35.27396 standard ounces. If you’re using troy ounces, the number is different: 1 kg ÷ 31.1035 = 32.1507 troy ounces. This distinction matters when comparing bulk prices in kilograms versus ounce-based pricing.

Quick conversion: 1 kg = 35.274 oz

For most practical purposes — cooking, shipping, nutrition — 1 kg equals about 35.27 standard ounces. Brite (online conversion tool) uses the exact factor 28.349523125 g/oz and reports the same figure. For gold, 1 kg holds roughly 32.15 troy ounces.

The trade-off: if you’re a baker buying flour in kilograms but your recipe calls for ounces, use the standard conversion. If you’re a bullion trader, use the troy conversion. Getting it wrong can mean a 10% error in either direction.

Is 4oz a 100g?

Exact grams in 4 ounces

4 standard ounces = 4 × 28.3495 = 113.398 grams. That’s 13.4% more than 100 g. The approximation “4 oz = 100 g” is a rough rounding used by some home cooks, but it’s not accurate enough for baking or nutrition labeling.

Why is 4 oz often called 100 g?

The confusion probably comes from the reverse approximation: 100 g is about 3.53 oz, which people sometimes round up to 4 oz. But in reality, 4 oz is closer to 113 g. Omni Calculator (science & measurement tool) provides the exact formula and warns against using the 100 g shortcut for precision.

Is 4 oz equal to 250 g?

No. 250 g is approximately 8.82 oz. 4 oz is about 113 g. The two have no relationship — a typo or mental slip might have created the confusion. Always use a conversion factor of 28.35 g per ounce for standard ounces.

The catch: “4 oz = 100 g” is a myth from rough recipe adaptation. For any purpose where weight matters — macro tracking, chemistry, shipping — use the exact 113.4 g figure.

What is 30 grams equal to?

30 grams to ounces

30 g divided by 28.3495 gives 1.0582 standard ounces. That’s just over 1 oz. If you’re working with gold or precious metals, 30 g is 0.9645 troy ounces — almost exactly one troy ounce (the extra 1.1 g makes the difference).

Common items that weigh 30 grams

In cooking, 30 g of all-purpose flour is about 1 tablespoon. A standard AA battery weighs roughly 23 g, so 30 g is a little more. A U.S. nickel coin is 5 g, so six nickels = 30 g. For gold, 30 g is slightly less than one troy ounce.

What this means: if you are across the pond and a recipe calls for 30 g of sugar, just use 1 oz (28.35 g) — the difference is trivial. But for precious metals, 30 g is not a full troy ounce.

Standard vs. Troy Ounce: Complete Comparison

Two ounces, one important difference. Here’s how they stack up side by side.

How to Convert Ounces to Grams: A Quick Guide

Step 1: Identify your ounce type

Check if you’re measuring food (use standard) or precious metals (use troy). Most recipes and grocery items use the avoirdupois system.

Step 2: Apply the correct conversion factor

• Standard ounces: multiply by 28.3495 (or 28.35 for cooking).
• Troy ounces: multiply by 31.1035 (or 31.10 for bullion).

Step 3: Use a calculator or our conversion cheat sheet

For quick reference, Omni Calculator (interactive conversion tool) lets you toggle between ounce types. The table in the “Key Facts” section above covers the most common conversions.

What’s Confirmed and What’s Still Open

Confirmed facts

• 1 standard ounce = 28.349523125 g (NIST HB 44 2024 Appendix C)
• 1 troy ounce = 31.1034768 g (NIST Precious Metals)
• 1 kg = 35.27396 standard oz (Brite)
• Troy ounce is 9.7% heavier than standard oz (U.S. Money Reserve)

What remains unclear

• Whether imported goods label “oz” as troy or avoirdupois without additional context — the U.S. does not mandate differentiation on consumer packaging.
• Rounding practices for nutrition labeling vary: some countries allow 28 g, others use 28.35 g.

Expert Voices on Ounce Conversions

“The avoirdupois ounce is defined as exactly 28.349523125 grams in the U.S. customary system.”

— National Institute of Standards and Technology (NIST) (U.S. government measurement authority)

“One troy ounce equals 31.1034768 grams. Gold prices are quoted per troy ounce in all major markets.”

— NIST Precious Metals Conversion Information (official U.S. conversion table)

“For cooking and everyday use, 1 oz = 28.35 g is precise enough for nutrition and recipes.”

— Brite (cooking conversion tool)

“A troy ounce is about 9.7% heavier than an avoirdupois ounce. This difference becomes critical when buying silver or gold.”

— U.S. Money Reserve (bullion education platform)

For home cooks or gold investors, the difference between 28.35 g and 31.1035 g per ounce can add up quickly. Using the wrong conversion could throw off a recipe by tablespoons or cost you money on a gold transaction. The fix is simple: always check whether your “oz” is standard or troy — and use the correct multiplier.

If you need a more detailed explanation, this detailed conversion guide covers both standard and troy ounce conversions.

Frequently asked questions