Troy Ounce vs Gram: The Complete Guide

If you’ve ever looked up a gold price, you’ve seen it quoted in troy ounces — not regular ounces, and not grams. This can be confusing at first, but there’s a reason precious metals use their own weight system that dates back centuries. This guide explains everything clearly.

What Is a Troy Ounce?

A troy ounce (symbol: oz t) is a unit of mass equal to 31.1035 grams. It is the standard unit of weight used for precious metals worldwide — gold, silver, platinum, and palladium are all quoted per troy ounce on global commodity exchanges.

Troy Ounce vs Regular Ounce

The two types of ounce are easy to confuse. Here is the key difference:

Unit	Grams	Used For
Troy ounce (oz t)	31.1035 g	Gold, silver, platinum, palladium
Avoirdupois ounce (oz)	28.3495 g	Everyday items, food, postal weight
Difference	+2.754 g	—

This distinction matters enormously when calculating gold values. If a dealer quotes you a price “per ounce” for gold, they always mean per troy ounce.

Where Does the Troy Ounce Come From?

The troy ounce is named after Troyes, a city in the Champagne region of France, which was home to one of the most important medieval trade fairs in Europe. The troy weight system was widely adopted by English merchants in the 15th century and was formally adopted in Britain in 1527 for precious metals. It has been the global standard for precious metals ever since.

The system persisted because standardisation in global commodities trading is critical — every buyer and seller worldwide uses troy ounces, ensuring consistency across markets from the London Bullion Market to the COMEX exchange in New York.

Complete Weight Conversion Table

Use this reference table to convert between all common precious metals weight units:

From	To Grams	To Troy Oz	To Kg	To Pennyweight
1 Troy Ounce	31.1035 g	1 oz t	0.031103 kg	20 dwt
1 Gram	1 g	0.03215 oz t	0.001 kg	0.6430 dwt
1 Kilogram	1000 g	32.1507 oz t	1 kg	643.015 dwt
1 Pennyweight	1.55517 g	0.05 oz t	0.001555 kg	1 dwt
1 Grain	0.0648 g	0.002083 oz t	0.0000648 kg	0.04167 dwt

What Is a Pennyweight?

A pennyweight (dwt) is a unit of weight equal to 1.55517 grams, or 1/20th of a troy ounce. It is commonly used by US jewellers and scrap gold dealers. If a dealer quotes you a price per pennyweight, multiply by 20 to get the equivalent troy ounce price, or divide by 0.6430 to get the per-gram price.

How to Convert Gold Spot Price From Troy Ounce to Gram

The gold spot price is always quoted per troy ounce on markets and financial sites. To get the price per gram:

For example: If gold is $3,300/oz → $3,300 ÷ 31.1035 = $106.09 per gram.

Our live calculator does this conversion automatically and updates every 60 seconds.

Troy Ounces in Gold Bars and Coins

Standard gold investment products are described in troy ounces:

• 400 troy oz — the Good Delivery bar, held by central banks (12.44 kg)
• 100 troy oz — large commercial bar (3.11 kg)
• 1 kilo bar — 32.1507 troy oz (popular in Asian markets)
• 1 troy oz coin — e.g. Krugerrand, American Eagle, Britannia (31.1035 g)
• 1/2 troy oz coin — 15.5518 g
• 1/4 troy oz coin — 7.7759 g