Calculating the true worth of gold items requires three main pieces of data: the total weight, the purity (karats), and the current market "spot price." This calculator simplifies the process by converting units and accounting for gold fineness automatically.
Understanding Gold Karats (Purity)
Gold is rarely used in its pure form for jewelry because it is too soft. It is mixed with alloys like copper or silver. The Karat (K) system measures the ratio of pure gold to other metals:
24K: 99.9% Pure gold.
18K: 75% Pure gold (18 parts gold, 6 parts alloy).
14K: 58.3% Pure gold (14 parts gold, 10 parts alloy).
10K: 41.7% Pure gold (The minimum standard for "gold" in the US).
The Calculation Formula
The math behind the valuation is as follows:
Value = (Weight in Troy Ounces) × (Karat / 24) × (Current Spot Price)
Practical Example
If you have a 14K gold ring weighing 10 grams and the market price is $2,000 per ounce:
Convert grams to troy ounces: 10g / 31.1035 = 0.3215 oz t.
Calculate purity decimal: 14 / 24 = 0.5833.
Multiply: 0.3215 × 0.5833 × $2,000 = $375.05.
Note: Professional buyers often pay 70% to 90% of the calculated "melt value" to account for refining costs and profit margins.
function calculateGoldValue() {
var weight = parseFloat(document.getElementById('goldWeight').value);
var unit = document.getElementById('weightUnit').value;
var karat = parseFloat(document.getElementById('goldPurity').value);
var spotPrice = parseFloat(document.getElementById('marketPrice').value);
var resultDiv = document.getElementById('goldResult');
var valueDisplay = document.getElementById('totalValue');
var detailDisplay = document.getElementById('purityBreakdown');
if (isNaN(weight) || isNaN(spotPrice) || weight <= 0 || spotPrice <= 0) {
alert("Please enter valid positive numbers for weight and market price.");
return;
}
// Convert weight to Troy Ounces (Standard market unit)
var weightInTroyOunces = 0;
if (unit === "grams") {
weightInTroyOunces = weight / 31.1034768;
} else if (unit === "ounces") {
weightInTroyOunces = weight;
} else if (unit === "kilograms") {
weightInTroyOunces = weight * 32.1507;
} else if (unit === "pennyweight") {
weightInTroyOunces = weight / 20;
}
// Calculate Fineness (Percentage of pure gold)
var fineness = karat / 24;
// Calculate Total Value
var totalValue = weightInTroyOunces * fineness * spotPrice;
var pureGoldWeight = weight * fineness;
// Display results
valueDisplay.innerHTML = "$" + totalValue.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2});
detailDisplay.innerHTML = "Your item contains approximately " + pureGoldWeight.toFixed(2) + " " + unit + " of pure gold content.";
resultDiv.style.display = "block";
resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}