The whole calculation in three lines
Everything on this page is the same three steps, and they are worth knowing without a calculator because they are short enough to check in your head:
- Pure gold weight = weight × karat ÷ 24.
- Price per gram of pure gold = spot price ÷ 31.1034768, if the price is per troy ounce.
- Melt value = pure gold weight × price per gram.
A 20 g chain stamped 14K: 20 × 14 ÷ 24 = 11.667 g of gold. At 3,000 per troy ounce, a gram of pure gold is 3,000 ÷ 31.1034768 = 96.4522. So 11.667 × 96.4522 = 1,125.28. That is the metal. It is not an offer, and the section on what a buyer pays explains the gap.
What karat actually means
Karat is a fraction with 24 on the bottom. It describes how much of the alloy’s mass is gold, and nothing else — not the colour, not the quality of the work, not the weight of the piece.
| Karat | Gold by mass | Fineness, as stamped |
|---|---|---|
| 24K | 100% | 999 |
| 22K | 91.667% | 916 |
| 21K | 87.5% | 875 |
| 18K | 75% | 750 |
| 14K | 58.333% | 585 |
| 10K | 41.667% | 417 |
| 9K | 37.5% | 375 |
The third column is where people get stuck. 14÷24 is 58.3333%, which is 583.33 parts per thousand — but European hallmarking stamps 585 and older American work stamps 583. A hallmark is a legal minimum fineness, set slightly above or below the arithmetic for reasons of assay tolerance and national law. It is not a different measurement of the same thing, and neither number is the mistake. This calculator works in the karat fraction you pick and shows the conventional stamp beside it.
Karat is also not carat. A carat is 200 mg and weighs gemstones. The two words are used interchangeably in some countries and mean entirely different things.
Grams, tola, troy ounces and the rest
Gold is weighed in a startling number of units, and every one of them is exact by definition rather than approximate. The grain is the root of all of them: 64.79891 mg, fixed by the 1959 international yard and pound agreement.
| Unit | In grams | Defined as |
|---|---|---|
| Grain | 0.06479891 | The base definition |
| Pennyweight (dwt) | 1.55517384 | 24 grains |
| Troy ounce (ozt) | 31.1034768 | 480 grains, or 20 dwt |
| Ounce, avoirdupois | 28.349523125 | 437.5 grains |
| Tola | 11.6638038 | Three eighths of a troy ounce |
| Baht (bar) | 15.244 | Thai gold bar standard |
The one to watch is the troy ounce against the ordinary ounce. They are both called an ounce, they differ by about 10%, and a kitchen scale reports the smaller one. Weigh gold in grams if you possibly can — the conversion is then a single multiplication and there is nothing to mix up.
The Thai baht appears twice in the unit list because it genuinely is two units. A baht of gold bar is 15.244 g; a baht of gold jewellery is sold at 15.16 g. The difference is small and it is real, so both are offered rather than one being quietly picked.
Spot price against a jeweller’s per-gram rate
This is the mistake that costs money. A spot price is a price for pure gold. A jeweller quoting a per-gram rate for 22K is pricing the alloy as weighed. The two are related by the purity and are not interchangeable.
Suppose a shop quotes 100 per gram for 22K. Ten grams of 22K is then 1,000 — straightforward, because the price and the weight are both of the same thing. But the pure gold in those ten grams is only 9.1667 g, so the shop is implicitly paying 100 ÷ (22÷24) = 109.09 per gram of pure gold. If you had typed 100 into a calculator expecting a spot price, you would have got 916.67 instead of 1,000 and concluded you were being short-changed.
The calculator asks which basis your figure uses and refuses to assume. It also refuses one case outright: an alloy-basis price alongside several pieces at different karats is ambiguous, because the price belongs to one purity and there is more than one on the table. Enter the pieces separately or switch to a spot price.
Several pieces at different karats
Weigh them separately. The combined purity of a lot is the total pure gold divided by the total weight, and that is not the average of the karat numbers unless the weights happen to be identical.
Thirty grams of 22K and ten grams of 14K: the 22K piece holds 30 × 22 ÷ 24 = 27.5 g of gold and the 14K piece holds 10 × 14 ÷ 24 = 5.833 g. That is 33.333 g of gold in 40 g of metal, which is 0.8333 — exactly 20K. Averaging 22 and 14 gives 18K, two karats light, and on this lot that error is worth about 8% of the value.
With equal weights the average does happen to work: 10 g of 22K and 10 g of 14K really is 18K. That coincidence is exactly why the shortcut survives.
What a buyer actually pays
Melt value is the ceiling, not the offer. Between the two sit a refiner’s loss, an assay, a shipping cost and the buyer’s margin — and the margin is set by the buyer, varies enormously between a pawnbroker, a high-street jeweller and a refiner taking a kilo at a time, and is not something any calculator can know.
What this page does instead is keep the three lines separate: melt value, the margin you were quoted as a percentage, and any flat testing or refining fee. If you enter a 20% margin and a fee of 15 against that 1,125.28 chain, you see 225.06 of margin, 15 of fee and 885.22 left — and you can take those numbers back to the counter and ask about each one.
On a small piece the flat fee can exceed the metal entirely. The calculator says so plainly rather than showing a negative number as though it were a price.
Before you trust the karat stamp
Everything above assumes the stamp is honest and the item is solid. Two things to rule out first.
Plated and gold-filled. Plating is a few microns and weighs essentially nothing; gold-filled carries a bonded layer that is a stated fraction of total weight — 1/20 12K, for example — rather than a karat of the whole. Entering the full weight of either at a karat produces a figure that is wrong by an order of magnitude. Marks to look for: GP, GF, HGE, RGP, or a fraction before the karat.
Unmarked or suspect. An acid test, an electronic tester or an XRF scan at a jeweller settles it in minutes, usually free if you are selling. Every figure on this page is only as good as the purity you type into it.
Where the arithmetic happens
In your browser. The engine behind this page is a JavaScript file
your browser downloads and runs locally, and the tests that check
it — 165 assertions covering every conversion factor and worked
example on this page — live in the project as
tests/gold-lib.test.js. Nothing you type is
transmitted, logged or stored, and there is no price feed to call
because there is no price.
Looking for the rate in India?
This calculator is deliberately currency-agnostic and price-free. If you are in India and want today's figure in rupees — with 916 and the 750 hallmark, the tola, the pavan and the bhori, and a rate card per gram and per ten grams — gold rate in India is the page for that. It carries an international reference figure with its source and timestamp shown, states plainly how far that sits below a jeweller's counter price, and has its own calculator for Indian units and Indian charges.
Frequently asked questions
How do I calculate the value of my gold?
Three steps. Weigh it, work out how much of that weight is actually gold, then multiply by a price per unit of pure gold. A 20 g chain stamped 14K is 14/24 gold by mass, which is 11.667 g of pure gold. At a price of 3,000 per troy ounce — 96.4522 per gram — that is 1,125.28 of gold. What a buyer offers you is that figure minus their margin and any testing or refining charge.
What does karat mean, exactly?
Karat is a fraction of 24 by mass. 24K is pure gold, 18K is 18/24 = 75% gold, 14K is 14/24 = 58.333%, and 9K is 9/24 = 37.5%. The rest of the weight is other metals — usually copper, silver, zinc or nickel — which is what makes the alloy hard enough to wear. Karat has nothing to do with carat, the unit used to weigh gemstones.
Why does my 14K ring say 585 when 14/24 is 583?
Because a hallmark is a legal minimum fineness, not the karat arithmetic. 14/24 comes to 583.33 parts per thousand; European hallmarking uses 585 and older American stamps use 583. Both describe the same nominal karat. This calculator keeps the two apart — it works in the karat fraction you choose and shows the conventional stamp beside it rather than quietly swapping one for the other.
Is a per-gram price the same as a spot price?
No, and confusing them is the single most common mistake in this calculation. A spot price is per unit of pure gold. A jeweller quoting "per gram for 22K" is pricing the alloy as weighed, which at 22K is 91.667% gold — so 100 per gram of 22K is 109.09 per gram of pure gold. The calculator asks which basis your price uses and will not guess.
How many grams are in a tola?
11.6638038 g exactly. The standard tola of India and Pakistan is defined as three eighths of a troy ounce, and a troy ounce is 31.1034768 g. The calculator converts between grams, kilograms, troy ounces, pennyweight, grains, avoirdupois ounces, tola, baht, masha and ratti, and every factor it uses is exact by definition rather than rounded.
What is a troy ounce and why is it different from a normal ounce?
A troy ounce is 31.1034768 g and is the unit precious metals are priced in. An ordinary avoirdupois ounce — the one on a kitchen scale — is 28.349523125 g. A troy ounce is about 10% heavier, so treating one as the other overstates or understates a value by roughly a tenth. Both are exact: 480 grains and 437.5 grains respectively, with the grain defined as 64.79891 mg.
I have several pieces at different karats. What is the combined karat?
Add up the pure gold in each piece and divide by the total weight — not the average of the karat numbers, which is only right when the weights happen to be equal. 30 g of 22K and 10 g of 14K holds 27.5 + 5.833 = 33.333 g of gold in 40 g, which is 20K. Averaging 22 and 14 would have told you 18K, and been wrong by two karats.
Why does this calculator not show the live gold price?
Because a price printed on a page is out of date within the hour, and a stale gold price is worse than none: it invites you to make a decision on a number nobody is quoting. Look up the current spot price wherever you normally would, type it in, and the arithmetic here is yours to check. Nothing you type is sent anywhere.
Will a shop pay me the melt value?
No. Melt value is what the metal in the item is worth at the price you entered. A buyer has to test, refine and resell it, and prices accordingly — the gap is theirs to set and varies widely between a pawnbroker, a jeweller and a refiner. The calculator keeps melt value, margin and any flat fee as three separate lines so you can see exactly what is being deducted, but it does not know and will not guess what any particular buyer offers.
Does this work for gold-plated or gold-filled items?
Not usefully. Plating is measured in microns and contributes almost nothing by weight, and gold-filled items carry a bonded layer that is a stated fraction of the total weight rather than a karat of the whole. Entering the full weight of either at a karat would give a wildly overstated figure. This calculator is for solid karat gold.
How accurate does my scale need to be?
For jewellery, 0.01 g. At a spot price around 3,000 per troy ounce, a gram of pure gold is roughly 96, so a tenth of a gram is about 10 and a hundredth is about 1. A kitchen scale reading to the nearest gram is enough for a rough idea and not enough to check a buyer's figure.
Are my numbers sent anywhere?
No. Every calculation on this page runs in JavaScript in your own browser. Nothing you type — weights, purities or the price you looked up — is transmitted or stored on a server.