How to Convert Ounces to Grams: Baking Precision, Avoirdupois & Troy Weights
Converting ounces (oz) to grams (g) is one of the most frequent kitchen, laboratory, and international shipping calculations. Whether you are following a European pastry recipe or verifying postage weights, precision matters.
Written by the Toolseza team · Updated 2026-10-31
The Exact Mathematical Conversion Factor
Under international international treaty standards established by the BIPM and NIST in 1959, one international avoirdupois ounce is defined as exactly 28.349523125 grams.
For quick kitchen estimations: 1 oz ≈ 28.35 g. If you have 4 ounces of butter, multiplying 4 × 28.35 yields 113.4 grams (which corresponds exactly to one standard US stick of butter).
Avoirdupois Ounces vs Troy Ounces (Gold & Silver)
A critical distinction that catches buyers unaware is the difference between kitchen ounces and bullion ounces. Everyday groceries use the Avoirdupois ounce (28.35 grams, 16 ounces per pound).
Precious metals (gold, silver, platinum) and gemstones are measured exclusively in Troy ounces (symbol: oz t or troy oz). One Troy ounce equals exactly 31.1034768 grams—making it roughly 9.7% heavier than a grocery ounce! If a dealer quotes gold at $2,000 per ounce, they mean 31.1 grams, not 28.35 grams.
Quick Reference Conversion Table for Everyday Cooking
• 1 oz = 28.35 g (approx 1 slice of bread or cheese)
• 2 oz = 56.70 g
• 3.5 oz = 100 g (standard benchmark for European nutrition labels)
• 4 oz = 113.4 g (1 stick of butter or 1/4 lb burger patty)
• 8 oz = 226.8 g (1/2 lb)
• 16 oz = 453.59 g (1 full imperial pound)
Why Weight Beats Volume in Baking
Measuring dry flour in volumetric cups can vary by up to 25% depending on how tightly packed the flour is. Weighing in grams eliminates inconsistencies entirely: 1 cup of all-purpose flour weighs approximately 120–125 grams (4.25–4.4 oz).