Silver prices are almost always quoted per troy ounce, not per ordinary ounce. That one word matters. A troy ounce is about 10% heavier than the ounce used for food and parcels, so mixing them up gives the wrong value. This guide explains what a troy ounce is, shows the key conversions, and walks through how to turn a troy ounce silver price into a price per gram or per kilo.
What is a troy ounce?
A troy ounce is the unit of weight used for precious metals. It is defined as exactly 31.1034768 grams. For everyday use, that rounds to 31.1035 grams, the figure CME Group uses in its COMEX silver futures rulebook.
By contrast, the ordinary “avoirdupois” ounce is 28.349523125 grams. So a troy ounce is roughly 1.097 avoirdupois ounces. In other words, if you weighed a one-troy-ounce silver coin on a kitchen scale, it would read about 1.1 oz.
The troy system also has its own pound. A troy pound contains 12 troy ounces, not 16. However, the troy pound is rarely used today. In practice, the silver market works in troy ounces, grams and kilograms.
Troy ounce silver conversion table
| From | To | Multiply by |
|---|---|---|
| Troy ounces | Grams | 31.1035 |
| Grams | Troy ounces | 0.032151 |
| Kilograms | Troy ounces | 32.1507 |
| Troy ounces | Kilograms | 0.0311035 |
| Troy ounces | Avoirdupois ounces | 1.09714 |
| Avoirdupois pounds | Troy ounces | 14.5833 |
Conversions are calculated from the exact definitions of 31.1034768 grams per troy ounce and 28.349523125 grams per avoirdupois ounce, then rounded.
How to convert a silver price per troy ounce
The same logic works for any price. To get a price per gram, divide the troy ounce price by 31.1035. To get a price per kilo, multiply the troy ounce price by 32.1507.
For example, take a hypothetical silver price of $30.00 per troy ounce. This figure is for illustration only, not a current or forecast price.
- Per gram: $30.00 ÷ 31.1035 = about $0.96
- Per kilogram: $30.00 × 32.1507 = about $964.52
- Per avoirdupois ounce: $30.00 ÷ 1.09714 = about $27.34
That last line shows why the unit matters. If a seller quoted $30 per ordinary ounce, you would actually be paying more per gram than the $30 troy ounce price suggests.
Why the troy ounce silver standard matters on a chart
Almost every silver price chart you will see is in US dollars per troy ounce. Both the LBMA silver price benchmark and COMEX futures use this unit, so charts from different sources can be compared directly. For more on how the daily benchmark is set, see our guide to the LBMA silver price.
However, some local markets quote silver per gram or per kilo instead. When you compare a local price with an international chart, convert first. Otherwise, you are not comparing like with like. It also helps to remember that retail prices include a premium over the chart price, which we explain in our guide to silver spot prices.
Common silver bar and coin sizes
Physical silver comes in standard weights. Most one-ounce coins and bars use the troy ounce. Larger bars often come in kilos or in 100 troy ounce sizes.
At the wholesale level, the London market trades large “Good Delivery” bars. According to the LBMA, bars produced from 1 January 2025 must contain between 900 and 1,100 troy ounces of silver, which is roughly 28 to 34 kilograms. Older bars in the former 750 to 1,100 ounce range remain acceptable. Each bar must also be at least 999.0 parts per thousand pure.
Similarly, one COMEX silver futures contract covers 5,000 troy ounces, according to CME Group’s rulebook. That is about 155.5 kilograms of silver.
Frequently asked questions
How many grams are in a troy ounce of silver?
One troy ounce is exactly 31.1034768 grams, usually rounded to 31.1035 grams.
How many troy ounces are in a kilo of silver?
A kilogram contains about 32.15 troy ounces.
Is a troy ounce heavier than a regular ounce?
Yes. A troy ounce is about 9.7% heavier than the avoirdupois ounce used for everyday goods.
Why is silver priced in troy ounces?
The troy ounce is the long-standing standard unit of the precious metals trade. As a result, the main benchmarks and exchanges all use it, which keeps prices comparable worldwide.
Sources
- CME Group: COMEX Rulebook, Chapter 112, Silver Futures
- LBMA: London Good Delivery, Gold and Silver
- LBMA: Good Delivery Rules, Technical Specifications
This article is general information, not financial advice. Example prices are for illustration only. Prices shown on any site may lag the live market, so check an official source before making any decision.
Written and reviewed by the SilverPriceCharts.com editorial team. Sources are linked above.