Gold Purity Calculator - Karat, Percentage, Touch & Tunch Online

Free Online Gold Purity Calculator (Karat ↔ Percentage ↔ Touch)

The Tooloogle Gold Purity Calculator converts in every direction between the four ways gold purity is reported around the world: karat (24K, 22K, 18K, 14K, 10K), purity percentage (99.9%, 91.6%, 75%, 58.5%, 41.7%), touch / tunch (the Indian-subcontinent terminology used by jewellers, 91.6 touch = 22K), and the 3-digit hallmark stamped on jewellery (999, 916, 750, 585, 375). Type any one value and the others appear instantly. Useful for jewellery buyers verifying a hallmark, sellers calculating melt value, jewellers quoting alloy compositions, investors evaluating bullion versus jewellery, and anyone who has ever looked at a 916 stamp on a gold chain and wondered what karat that actually is.

What It Does & How It Works

Gold purity is the same physical quantity whether you call it karat, percentage, touch, or hallmark — the four are just different scales for measuring how much of the metal is actual gold versus the alloy metals (typically copper, silver, zinc, or palladium) added for hardness and color. The calculator runs all conversions through the single underlying ratio — pure-gold mass divided by total mass — so the karat number, the percentage, the touch value, and the hallmark stamp all stay synchronized as you edit any one of them. Enter the total weight of a piece in grams and the calculator also shows the pure-gold weight in grams, troy ounces, and standard ounces, useful when comparing scrap value or melt prices against the bullion market.

Features

• Bidirectional conversion — karat ↔ percentage ↔ touch/tunch ↔ hallmark mark, all live as you type.

• Common karat presets — 24K (999), 22K (916), 21K (875), 20K (833), 18K (750), 14K (583), 12K (500), 10K (417), 9K (375), 8K (333). One click per preset.

• Pure gold weight — enter total weight in grams; see pure-gold mass in grams, troy ounces, and avoirdupois ounces.

• Indian touch/tunch terminology — jewellers in India and South Asia quote purity in "touch" (91.6 touch = 22K, 75 touch = 18K, etc.). The calculator shows touch values alongside karat for every conversion.

• BIS hallmark mapping — instantly see whether your value corresponds to the standard BIS-certified marks (999, 958, 916, 875, 750, 585, 375).

• Live, browser-only — no upload, no signup, no analytics on what you calculate. Safe for valuing inherited jewellery, evaluating private investments, or assessing items under NDA.

Quick Reference: Karat ↔ Purity Percentage ↔ Hallmark ↔ Touch

The most-asked-for conversions in one table. Karat values are rounded to standard tradeable purities.

How to Use the Gold Purity Calculator

1. Enter a karat value in the karat field — the purity percentage, touch, and hallmark mark all update instantly.

2. Or enter a percentage in the purity field — the equivalent karat (rounded to nearest tradeable value), touch, and hallmark all update.

3. Or enter a touch value if your jeweller quoted in touch or tunch (Indian/South-Asian terminology) — karat and percentage update accordingly.

4. Or pick a preset — tap a preset chip (24K, 22K, 18K, 14K, 10K) to load that purity instantly.

5. (Optional) Enter the total weight in grams — the calculator shows the pure-gold weight in grams and troy ounces, useful for melt-value or scrap-purchase decisions.

6. Read off whichever value you need — the karat for jewellery shopping, the percentage for valuation conversations, the touch for South-Asian retailers, or the hallmark to verify a stamp on a piece you already own.

The Karat Formula (And Why 24 Is "Pure")

The karat scale uses 24 as the base for pure gold — not because 24 is significant numerically, but for historical reasons: a Roman gold solidus weighed exactly 24 carats (where a "carat" was a small carob seed used as a weight unit). When the term was later applied to purity instead of weight, the 24-base stuck. The formula:

Purity % = (Karat / 24) × 100

And the inverse:

Karat = (Purity % / 100) × 24

So 18K is (18 / 24) × 100 = 75% pure; 22K is (22 / 24) × 100 = 91.66...% pure (rounded to 91.6 in everyday use, which is why 22K jewellery is hallmarked "916"). Going the other way, 60% pure gold is (60 / 100) × 24 = 14.4 karat — usually rounded down to 14K for trade purposes.

The 3-Digit Hallmark Decoded

The 3-digit hallmark (999, 916, 750, 585, 375) is just the purity percentage written as parts-per-thousand instead of parts-per-hundred. Move the decimal point one place: 99.9% becomes 999, 91.6% becomes 916, 75% becomes 750, 58.5% becomes 585, 37.5% becomes 375. The hallmark is the international standard format used by the European Union, India's BIS (Bureau of Indian Standards), and most modern jewellery-stamping authorities, because it's unambiguous across languages and avoids fractional karat numbers.

What "Touch" and "Tunch" Mean

In the Indian subcontinent, jewellers traditionally quote purity in "touch" (sometimes spelled "tunch" or "tanch" depending on regional language) — the same number as the percentage but without the "%" sign. So 91.6 touch is 22K (91.6% pure), 75 touch is 18K (75% pure), and 99.9 touch is 24K (99.9% pure). When a jeweller in Mumbai, Chennai, Delhi, Lahore, or Dhaka tells you the gold is "91.6 touch", they mean BIS-916 hallmarked 22K. When they say "the alloy is 75 touch", they mean 18K (750 hallmark). The Tooloogle calculator displays touch values alongside karat, so the conversion is one glance regardless of which terminology your jeweller uses.

Common Conversion Examples

How to Calculate Karat From a Percentage

You see "88% gold" on a private-sale listing. What karat is that? Apply the formula: 88 / 100 × 24 = 21.12. So 88% gold corresponds to roughly 21K. Common percentages and their karat equivalents:

• 65% gold → 15.6 karat (sold as 15K or 16K)

• 71% gold → 17.04 karat (sold as 17K)

• 73% gold → 17.5 karat (sold as 17K or 18K)

• 74% gold → 17.76 karat (close to 18K)

• 80% gold → 19.2 karat (sold as 19K)

• 81% gold → 19.44 karat (sold as 19K)

• 82% gold → 19.68 karat (close to 20K)

• 85% gold → 20.4 karat (sold as 20K)

• 87% gold → 20.88 karat (close to 21K)

• 88% gold → 21.12 karat (sold as 21K)

• 91.6% gold → 22 karat (BIS-916 hallmark)

How to Calculate Percentage From a Karat

You inherited a 19K gold ring — what's the purity percentage? Apply the inverse formula: 19 / 24 × 100 = 79.17%. Common karats and their percentages:

• 16K → 66.7%

• 18K → 75% (hallmark 750)

• 19K → 79.2%

• 19.5K → 81.25%

• 20K → 83.3%

• 21K → 87.5% (hallmark 875)

• 21.5K → 89.6%

• 22K → 91.6% (hallmark 916)

• 23K → 95.8% (hallmark 958)

• 23.5K → 97.9%

• 24K → 99.9% (hallmark 999)

Common Conversions Between Common Karats

• 22K to 24K conversion: 1 gram of 22K (91.6% pure) contains 0.916 grams of pure gold — equivalent to 0.916 grams of 24K.

• 18K to 24K conversion: 1 gram of 18K (75% pure) contains 0.75 grams of pure gold — equivalent to 0.75 grams of 24K.

• 14K to 24K conversion: 1 gram of 14K (58.5% pure) contains 0.585 grams of pure gold.

• 10K to 24K conversion: 1 gram of 10K (41.7% pure) contains 0.417 grams of pure gold.

• 916 to 22K: same thing — the 916 hallmark is the European/BIS notation for 22K (91.6%).

• 750 to 18K: same thing — the 750 hallmark is 18K (75%).

• Pure gold to 916 conversion: divide by 0.916. So 10 grams of pure gold equals 10 / 0.916 = 10.92 grams of 916 (22K) alloy.

Pure-Gold Weight in Common Pieces

• 4 grams of 18K gold: 4 × 0.75 = 3 grams of pure gold.

• 9 grams of 10K gold: 9 × 0.417 = 3.75 grams of pure gold.

• 13 grams of 18K gold: 13 × 0.75 = 9.75 grams of pure gold.

• 18 grams of 10K gold: 18 × 0.417 = 7.51 grams of pure gold.

• 36 grams of 14K gold: 36 × 0.585 = 21.06 grams of pure gold.

• 1 troy ounce of 22K gold: 31.1035 × 0.916 = 28.49 grams of pure gold.

Common Use Cases

Verifying a hallmark on a piece of jewellery you bought or inherited — the calculator confirms what 750 / 916 / 999 actually means. Calculating the melt value of scrap gold before selling to a buyer — multiply the pure-gold weight by the current spot price. Comparing pricing across stores that quote in different scales (one shop quotes touch, the other quotes karat, a third quotes hallmark). Translating between Indian retail terminology ("91.6 touch") and European/American terminology ("22K" or "916"). Estimating customs duty on imported gold jewellery (most jurisdictions tax on pure-gold weight, not total alloy weight). Sanity-checking a jeweller's quote when you're buying or selling. Converting historical or international purity ratings (Russian/Soviet 583 is 14K; old British 9K is hallmark 375). Negotiating heirloom valuations during estate planning. Filing insurance claims that require pure-gold weight rather than total weight. Calculating gold-content tax for asset declarations.

How Karats Map to Color, Hardness, and Use

Higher karat (more pure gold) means softer, more yellow, and more expensive per gram. Lower karat (more alloy) means harder, more durable, and cheaper. The tradeoff explains why different markets use different standard purities:

• 24K (99.9%): too soft for daily-wear jewellery; primarily used for investment bars and coins, and for the deep-yellow Asian wedding jewellery where the buyer wants maximum gold content and accepts that the pieces are display, not daily-wear.

• 22K (91.6%): the dominant Indian-subcontinent and Middle-East wedding-jewellery purity. Soft but harder than 24K; rich yellow color; high resale value because the pure-gold content is high.

• 18K (75%): the dominant European fine-jewellery purity. Good color, much harder than 22K, suitable for everyday wear including engagement rings.

• 14K (58.5%): the dominant US mass-market purity. Significantly harder than 18K; lighter color (more alloy); the practical sweet-spot for daily-wear pieces.

• 10K (41.7%): the legal minimum for "gold" jewellery in the United States; common in inexpensive chains, costume pieces, and class rings. Very durable; pale color.

• 9K (37.5%): the legal minimum for "gold" jewellery in the United Kingdom and several Commonwealth countries.

• White, rose, and green gold: the same purity scale applies regardless of color. The color comes from the alloy choice (palladium / nickel for white, copper for rose, silver for green), but the karat number tells you only the gold content, not the alloy composition.

How to Calculate Gold Touch in Real Life

If a jeweller offers you a piece without a hallmark, the touch can be tested with: (1) acid testing — the most common in-store method, where a small streak of the gold is rubbed on a touchstone and reacted with nitric acid of known concentrations to estimate karat; (2) electronic testing using a hand-held XRF (X-ray fluorescence) gun, which gives a precise percentage; (3) density testing using an Archimedes-style scale, accurate but tedious. Once you have a measured percentage from any of those methods, the Tooloogle calculator converts it to karat, touch, and hallmark in one step.

Privacy & Browser-Based Processing

The Tooloogle Gold Purity Calculator runs entirely in your browser using basic arithmetic — no values are uploaded, no analytics is recorded on your inputs, no signup is required. This matters when valuing inherited jewellery, evaluating private investments, or doing pre-sale assessments where you don't want a third party to know what you own. Verify with browser DevTools that no requests fire as you type or compute.

Why Choose Tooloogle's Gold Purity Calculator?

Tooloogle's calculator is the only one that handles all four purity scales (karat, percentage, touch/tunch, hallmark) bidirectionally in one view. Indian and South-Asian users get touch terminology alongside karat without switching between tools. European and Indian users get the 3-digit hallmark mapping (916, 750, 585, 375) cross-referenced to karat. American users get the karat scale they're familiar with. Investors get the pure-gold weight in grams and troy ounces for melt-value calculations. Browser-only processing keeps your jewellery valuations private. Bookmark the page next to your safe-deposit-box inventory, your insurance-policy paperwork, or your jewellery-buying browser tab. Pair the calculator with the Tooloogle Currency Formatter when computing pricing in multiple currencies, the Discount Calculator when modeling alloy mixes or jeweller markup, and the Compound Interest Calculator when projecting the long-term return on a gold investment.