How to Convert Ounces to Grams

4 min read•June 1, 2025•Reviewed: June 1, 2026

✓Reviewed by Apex Conversion Editorial Team · Last reviewed June 1, 2026

Converting ounces to grams is straightforward: multiply the ounce value by 28.3495. The result is the exact gram weight. For a quick mental estimate, multiplying by 28 or 30 is close enough for most cooking and everyday uses.

This conversion is most useful when a US recipe specifies ounces but your kitchen scale reads grams, or when comparing US and European product weights. The key anchor: 1 oz = 28.35 g, so 4 oz = 113.4 g, 8 oz = 226.8 g, 16 oz = 453.6 g (1 lb).

Step-by-Step Instructions

Step 1: Identify the ounce value. Make sure it is in weight ounces (oz), not fluid ounces (fl oz). Step 2: Multiply by 28.3495. For a quick estimate, multiply by 28 instead. Step 3: Round to the nearest gram for cooking, or nearest 0.1 g for nutrition.

Example: US recipe calls for 6 oz of chocolate. Calculation: 6 × 28.3495 = 170.1 g. Round to 170 g. Alternatively: 6 × 28 = 168 g (close enough). The exact answer and the estimate differ by only 2 g on a 170 g total.

Worked Examples

US recipe: 2 oz butter
  2 × 28.3495 = 56.7 g

Package weight: 10.5 oz cereal
  10.5 × 28.3495 = 297.7 g  (≈ 298 g)

Protein portion: 3.5 oz chicken breast
  3.5 × 28.3495 = 99.2 g  (≈ 100 g)

Cheese serving: 1.5 oz cheddar
  1.5 × 28.3495 = 42.5 g

Quick estimate method (multiply by 28):
  6 oz × 28 = 168 g  (exact: 170.1 g — off by 1.2%)

Adapting US Recipes to Metric

US baking recipes typically list dry ingredients in volume (cups) or weight (ounces). When converting to metric for a kitchen scale, the ounce-to-gram step is essential. Common values: 1 oz flour ≈ 28 g, 1 oz butter = 28.35 g, 1 oz chocolate = 28.35 g, 1 oz sugar ≈ 28 g.

Packaged products often show both units: '12 oz (340 g)'. These labels use rounded values — 12 × 28.3495 = 340.19 g, rounded to 340 g. When adapting recipes from weight labels, use the gram value printed on the package rather than recalculating from ounces.

Quick Tips

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Multiply by 28 for a fast estimate — within 1.2% of the exact value.
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For 1 oz servings: round to 28 g on labels; use 28.35 for precise calculations.
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4 oz = 113.4 g — the quarter-pound reference most useful in protein/meat portioning.
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8 oz = 226.8 g — half a pound, the most common mid-size food package.
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If measuring with a food scale, weigh in grams directly — no conversion needed.

Frequently Asked Questions

What is 3 oz in grams?

3 × 28.3495 = 85.05 g — approximately 85 g. This is the standard 3 oz serving size often shown on US nutrition labels.

What is 12 oz in grams?

12 × 28.3495 = 340.19 g — approximately 340 g. A standard US pasta package is 12 oz (340 g).

Can I use 30 instead of 28.35 for a quick estimate?

Yes — multiplying by 30 is fast but gives a result about 5.8% too high. For 8 oz: 8 × 30 = 240 g vs. the exact 226.8 g. Use 28 for a closer (but still rounded) estimate.

What is a fluid ounce in grams?

A fluid ounce is a volume unit (≈ 29.57 mL), not a weight unit. The weight of 1 fl oz depends on the liquid's density: water ≈ 29.6 g, milk ≈ 30.5 g, honey ≈ 42.5 g.

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