How Many Grams in an Ounce of Gold? (Troy Ounce to Gram Guide)

One troy ounce of gold equals approximately 31.1035 grams, which is heavier than the regular kitchen ounce of about 28.35 grams.

Gold is usually priced per ounce in global markets, but in many countries, including India, everyday buyers and jewellers think in grams. If you do not know how many grams are in an ounce of gold, it becomes difficult to compare prices, understand purity, or calculate the exact value of your jewellery or investment. A clear understanding of this conversion helps you avoid confusion, negotiate better, and make informed buying or selling decisions. This guide explains the exact conversion, why a troy ounce is used, and how you can convert both ways quickly and accurately.

Basic answer: grams in one ounce of gold

For gold and other precious metals, the standard unit is the troy ounce, not the regular kitchen ounce. The exact and widely accepted conversion is:

• 1 troy ounce of gold = 31.1035 grams (often rounded to 31.1 g)
• 1 standard (avoirdupois) ounce = 28.3495 grams (used for food and everyday items, not gold pricing)

So, whenever you see gold quoted as “per ounce” on bullion websites, financial news, or trading platforms, it is referring to the troy ounce of about 31.1035 grams.

Troy ounce vs regular ounce (avoirdupois)

Many people assume all ounces are the same, but in gold trading that assumption leads to mistakes. There are two main types of ounces you should know:

• Troy ounce (used for gold, silver, platinum, and other precious metals)
• Avoirdupois ounce (used for groceries, cooking, and most everyday goods)

Here is a simple comparison:

Unit type	Used for	Exact grams per ounce	Notes
Troy ounce (oz t)	Gold, silver, platinum, precious metals	31.1035 g	Standard in global bullion markets and gold price quotations.
Avoirdupois ounce	Food, packages, household items	28.3495 g	Lighter; common in US customary system (kitchen scales, etc.).

Because a troy ounce is heavier than a regular ounce, confusing the two will give you the wrong gram value and can distort price calculations.

Why gold uses the troy ounce

The troy ounce comes from an old European system of weights used in trade fairs, particularly in the French city of Troyes, where merchants needed a consistent standard for precious goods. Over time, this unit became the accepted global standard for gold, silver, and other precious metals because it offered a reliable, precise measurement for high‑value materials. Today, international gold prices on exchanges and bullion dealers’ websites are almost always quoted in troy ounces, not grams or regular ounces.

Using a single, globally accepted unit (the troy ounce) makes it easier for traders, investors, and jewellers in different countries to compare prices and execute trades fairly. When you convert that troy ounce into grams, the number 31.1035 becomes the key to understanding the weight behind each quoted price.

Exact conversion formulas (ounce ⇄ gram for gold)

To work confidently with gold weights, you can use two simple formulas based on the troy ounce system.

1. Ounces of gold to grams

Use this when the weight is given in ounces and you want grams:

• Grams = Ounces × 31.1035

Example: If you have 2 troy ounces of gold:
Grams = 2 × 31.1035 = 62.207 grams.

2. Grams of gold to ounces

Use this when you know the grams (common in jewellery bills) and want to know ounces:

• Ounces = Grams ÷ 31.1035

Example: If you have 50 grams of gold:
Ounces ≈ 50 ÷ 31.1035 ≈ 1.6075 troy ounces.

Memorizing just one number—31.1035—helps you convert in either direction quickly and accurately.

Quick reference: common ounce–gram values for gold

Here are some common troy ounce quantities and their equivalent weights in grams, useful for investors and buyers.

Troy ounces of gold	Grams (approx.)
0.25 oz	7.776 g
0.5 oz	15.552 g
1 oz	31.1035 g
2 oz	62.207 g
5 oz	155.5175 g
10 oz	311.035 g

Similarly, if you often handle gold in grams, this basic mapping can guide you when thinking in ounces.

Grams of gold	Troy ounces (approx.)
10 g	0.3215 oz
20 g	0.6430 oz
30 g	0.9645 oz
31.1035 g	1 oz
50 g	1.6075 oz
100 g	3.2150 oz

These approximations are accurate enough for everyday understanding, but financial transactions often use full precision.

How purity (karat) affects gold value, not grams

The conversion between troy ounces and grams depends only on weight, not purity. However, the actual value you receive for gold also depends on its fineness or karat rating. For example:

• 24‑karat gold is considered pure (99.9% or higher).
• 22‑karat gold is about 91.67% pure (common in jewellery in India and many other countries).

If you have 31.1035 grams of 22K gold, it still weighs 1 troy ounce, but the pure gold content is lower than a 1‑ounce piece of 24K bullion. Buyers and lenders therefore apply a purity factor when deciding the price, even though the gram or ounce weight remains the same.

Practical examples for investors and jewellery buyers

Understanding this conversion is especially helpful in real‑world situations such as investing in coins, buying jewellery, or taking a gold loan.

• If a bullion dealer lists a 1‑ounce gold coin, it usually means about 31.1035 grams of fine gold.
• Some coins, like certain modern bullion coins, are labelled in grams (for example, 30 g), so you may want to convert to ounces to compare prices with 1‑ounce coins.
• In India, where gold is often sold and pledged in grams, knowing that 1 troy ounce = 31.1035 grams helps you compare local gram‑based prices with international ounce‑based market rates.

If you are checking live gold prices quoted “per ounce” on global sites while your jeweller quotes “per gram,” this conversion is the crucial bridge between the two.

Common mistakes to avoid when converting

Even small misunderstandings can lead to noticeable price differences when dealing with gold.

• Using the regular ounce (28.3495 g) instead of the troy ounce (31.1035 g) for gold calculations.
• Rounding too early, such as using 31 g instead of 31.1035 g in large transactions, which can add up over many ounces.
• Ignoring purity (karat) while comparing prices, assuming all 1‑ounce or 31.1‑gram items have identical value.
• Mixing up grams and troy ounces when reading coins or bar specifications, especially on international sites.

Being precise about which ounce you are using and how you convert helps you protect your money and make fair comparisons.

How to remember the conversion easily

For day‑to‑day use, you do not need to remember many numbers—one key figure and a simple mental trick can be enough.

• Remember: 1 troy ounce of gold ≈ 31.1 grams.
• Think: “a gold ounce is a bit more than 31 grams, not 28 grams like the regular ounce.”
• For a quick estimate, you can treat 30 grams as “almost 1 ounce of gold,” but rely on 31.1035 grams for accurate calculation.

Investors who frequently trade gold often keep a small list or use a converter app or website, but knowing the core number still gives you confidence when you are away from tools.

FAQs about grams in an ounce of gold