Calculate Gold Weight

Understanding Gold Weight Calculation

Calculating the precise weight of gold is essential for various purposes, whether you're a jeweler, an investor, or simply curious about a piece of gold you own. This calculator helps you determine the weight of gold based on its volume and purity (karat).

The Science Behind Gold Weight

Gold's weight is primarily determined by two factors: its volume and its density. Pure gold has a specific density, and when mixed with other metals (to form alloys for durability or color), its overall density and thus its weight for a given volume changes based on its purity.

1. Gold Purity (Karat)

Gold purity is measured in karats (K). 24-karat gold is considered 100% pure. Lower karat numbers indicate a gold alloy, meaning gold is mixed with other metals like copper, silver, or zinc. For example:

  • 24K Gold: 100% pure gold.
  • 22K Gold: Contains 22 parts gold and 2 parts other metals (91.67% pure).
  • 18K Gold: Contains 18 parts gold and 6 parts other metals (75% pure).
  • 14K Gold: Contains 14 parts gold and 10 parts other metals (58.33% pure).
  • 10K Gold: Contains 10 parts gold and 14 parts other metals (41.67% pure).

The purity percentage directly impacts the gold's actual weight for a given volume, as the other metals in the alloy typically have different densities than pure gold. Our calculator uses the standard density of pure gold and then adjusts for the purity percentage.

2. Gold Volume (cm³)

Volume is the amount of space an object occupies. For gold, it's typically measured in cubic centimeters (cm³). If you have a regularly shaped gold item (like a bar, sphere, or cylinder), you can calculate its volume using standard geometric formulas:

  • Rectangular Bar: Length × Width × Height
  • Cylinder: π × Radius² × Height
  • Sphere: (4/3) × π × Radius³

For irregularly shaped items, specialized methods like water displacement (Archimedes' principle) can be used to determine volume.

3. Density of Pure Gold

The density of pure gold (24K) is approximately 19.3 grams per cubic centimeter (g/cm³). This means that one cubic centimeter of pure gold weighs 19.3 grams. This is a fundamental constant used in our calculation.

How the Calculator Works

The calculator takes your specified gold purity and its volume to determine its total weight. The formula used is:

Gold Weight (grams) = Gold Volume (cm³) × Density of Pure Gold (g/cm³) × (Purity Percentage / 100)

The result is then converted into common units like grams, troy ounces, and kilograms for your convenience.

Example Calculation

Let's say you have a gold bar with a volume of 10 cm³ and it's made of 18K gold.

  • Gold Volume: 10 cm³
  • Gold Purity: 18K (which is 75% pure)
  • Density of Pure Gold: 19.3 g/cm³

Using the formula:

Gold Weight (grams) = 10 cm³ × 19.3 g/cm³ × (75 / 100)

Gold Weight (grams) = 10 × 19.3 × 0.75

Gold Weight (grams) = 144.75 grams

This 144.75 grams would then be converted to troy ounces and kilograms by the calculator.

Gold Weight Calculator

24K (100% Pure) 22K (91.67% Pure) 18K (75% Pure) 14K (58.33% Pure) 10K (41.67% Pure) Custom Purity

Your Gold Weight:

Grams: —

Troy Ounces: —

Kilograms: —

function toggleCustomPurity() { var purityKarat = document.getElementById("goldPurityKarat").value; var customPurityDiv = document.getElementById("customPurityDiv"); if (purityKarat === "custom") { customPurityDiv.style.display = "block"; } else { customPurityDiv.style.display = "none"; } } function calculateGoldWeight() { var goldPurityKarat = document.getElementById("goldPurityKarat").value; var customPurityPercentageInput = document.getElementById("customPurityPercentage"); var goldVolumeInput = document.getElementById("goldVolume"); var goldWeightResultDiv = document.getElementById("goldWeightResult"); var goldVolume = parseFloat(goldVolumeInput.value); var purityPercentage; // Reset result div styling goldWeightResultDiv.style.backgroundColor = "#e9f7ef"; goldWeightResultDiv.style.color = "#155724"; // Validate Gold Volume if (isNaN(goldVolume) || goldVolume <= 0) { goldWeightResultDiv.style.backgroundColor = "#f8d7da"; goldWeightResultDiv.style.color = "#721c24"; goldWeightResultDiv.innerHTML = "Please enter a valid positive Gold Volume (cm³)."; return; } // Determine Purity Percentage if (goldPurityKarat === "custom") { purityPercentage = parseFloat(customPurityPercentageInput.value); if (isNaN(purityPercentage) || purityPercentage 100) { goldWeightResultDiv.style.backgroundColor = "#f8d7da"; goldWeightResultDiv.style.color = "#721c24"; goldWeightResultDiv.innerHTML = "Please enter a valid Custom Purity percentage (0.01-100%)."; return; } } else { var karatValue = parseFloat(goldPurityKarat); if (isNaN(karatValue) || karatValue <= 0) { // Should not happen with dropdown, but good for robustness goldWeightResultDiv.style.backgroundColor = "#f8d7da"; goldWeightResultDiv.style.color = "#721c24"; goldWeightResultDiv.innerHTML = "Invalid Karat selection."; return; } purityPercentage = (karatValue / 24) * 100; } // Constants var densityPureGold = 19.3; // g/cm³ var troyOunceToGram = 31.1035; // 1 troy ounce = 31.1035 grams // Calculate Gold Weight in Grams var goldWeightGrams = goldVolume * densityPureGold * (purityPercentage / 100); // Convert to other units var goldWeightTroyOunces = goldWeightGrams / troyOunceToGram; var goldWeightKilograms = goldWeightGrams / 1000; // Display Results document.getElementById("resultGrams").innerHTML = "Grams: " + goldWeightGrams.toFixed(2) + " g"; document.getElementById("resultTroyOunces").innerHTML = "Troy Ounces: " + goldWeightTroyOunces.toFixed(2) + " ozt"; document.getElementById("resultKilograms").innerHTML = "Kilograms: " + goldWeightKilograms.toFixed(3) + " kg"; } // Initialize custom purity div visibility on page load document.addEventListener('DOMContentLoaded', function() { toggleCustomPurity(); });

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