Online Gold Purity Calculator – Assess Your Gold’s Value

What Does This Calculator Do?

Not all gold is created equal. A piece of jewelry stamped 22K contains significantly more pure gold than one marked 18K, and knowing exactly how much pure gold you’re actually dealing with — and what it’s worth at today’s market price — matters whether you’re buying, selling, investing, or simply trying to understand what you own. This Gold Purity Calculator gives you all of that information in one place, instantly, without needing a jeweler or a complex spreadsheet.

You enter the total weight of the gold item, specify its purity either in karats or as a percentage, and optionally add the current market price per gram. The calculator then tells you the exact purity as both a karat value and a percentage, the weight of pure gold contained in the item, and — if you’ve entered a market price — the estimated monetary value of that pure gold content. A purity progress bar gives you a visual representation of how pure the gold is relative to 100%, and a detailed breakdown table lists every calculated metric clearly so you have the full picture in one view.

The Formula Behind It

Purity Conversion — Karat to Percentage:

The karat system divides gold purity into 24 parts. Pure gold is 24 karats, meaning it is 24 out of 24 parts gold. The purity percentage is calculated as:

Purity % = (Karat ÷ 24) × 100

Common karat values and their purity percentages:

If you enter purity as a percentage directly instead of karats, the equivalent karat value is calculated as:

Karat = (Percentage ÷ 100) × 24

Pure Gold Weight:

Once purity is known, the weight of actual pure gold in the item is:

Pure Gold Weight = Total Weight (in grams) × (Purity % ÷ 100)

For example, a 10-gram piece of 22K gold:

• Purity = (22 ÷ 24) × 100 = 91.67%
• Pure Gold Weight = 10 × 0.9167 = 9.167 grams of pure gold

Unit Conversions:

The calculator automatically converts all weight inputs to grams before calculating:

• Troy Ounces to grams: 1 troy oz = 31.1035 grams
• Kilograms to grams: 1 kg = 1,000 grams

Gold Value:

If a market price per gram is entered, the estimated value is:

Gold Value = Pure Gold Weight (grams) × Market Price (per gram)

Using the example above with a market price of $90/gram:

• Gold Value = 9.167 × 90 = $825.03

How to Use It

The calculation takes just seconds:

1. Enter the Total Weight of your gold item and select the unit — grams, troy ounces, or kilograms
2. Enter the Gold Purity and toggle between Karat or Percentage depending on what’s stamped or known
3. Optionally enter the Market Price per gram if you want to calculate the monetary value
4. Click Calculate
5. Review the purity percentage, karat equivalent, pure gold weight, estimated value, the breakdown table, and the purity progress bar

Why It’s Worth Using

Gold transactions — whether buying jewelry, selling inherited pieces, investing in bullion, or appraising items — all hinge on understanding exactly how much pure gold is present and what that gold is worth. The karat stamp on a piece of jewelry tells you the purity grade, but it doesn’t immediately tell you how many grams of actual gold you’re holding or what those grams are worth at today’s price. This calculator bridges that gap instantly.

It’s particularly useful for anyone dealing with non-standard weights or purity inputs. Not everyone measures in grams — traders in different markets work in troy ounces, and large transactions may be quoted in kilograms. The automatic unit conversion means you can enter whatever unit you’re working with and get a consistent, accurate result without having to manually convert first.

The optional market price field also makes it easy to quickly check whether a gold price you’ve been quoted for buying or selling is in the right ballpark — giving you a simple sanity check before making any transaction.