Quick answer
A troy ounce is 31.1034768 grams. A regular household ounce is about 28.3495 grams. Precious metals use troy ounces, so using regular ounces will understate metal weight by about 9%.
The key conversions
One troy ounce equals 31.1034768 grams.
One troy ounce equals 20 pennyweights or 480 grains.
One regular avoirdupois ounce equals about 28.3495 grams.
Why it matters
Gold, silver, platinum, and palladium spot prices are quoted per troy ounce.
If you enter a regular ounce weight as a troy ounce weight, your estimate will be off.
Best practical workflow
Use a gram scale, convert grams to troy ounces, then apply purity and spot price.
Round at the end rather than rounding each intermediate conversion.
FAQ
Common questions
How many grams are in a troy ounce?
One troy ounce equals 31.1034768 grams.
How many pennyweights are in a troy ounce?
One troy ounce equals 20 pennyweights.
Sources