Gold Price Calculator
A gold price calculator determines the value of gold based on weight, purity, and current spot price. Gold is measured in troy ounces (31.1 grams), and purity is expressed in karats or fineness.
Gold Weight Conversions
| Unit | Grams | Troy Ounces |
|---|---|---|
| 1 Gram | 1 | 0.0322 |
| 1 Troy Ounce | 31.1035 | 1 |
| 1 Regular Ounce | 28.3495 | 0.911 |
| 1 Kilogram | 1,000 | 32.15 |
Gold Purity (Karat) Values
| Karat | Purity | Gold Content |
|---|---|---|
| 24K | 99.9% | Pure gold |
| 22K | 91.7% | Jewelry grade |
| 18K | 75.0% | Common jewelry |
| 14K | 58.3% | Popular US standard |
| 10K | 41.7% | Minimum for "gold" |
Gold Value Examples
At $2,000/troy ounce spot price:
| Weight | 24K Value | 18K Value | 14K Value |
|---|---|---|---|
| 1 gram | $64.30 | $48.23 | $37.48 |
| 5 grams | $321.50 | $241.13 | $187.42 |
| 1 troy oz | $2,000 | $1,500 | $1,166 |
| 10 grams | $643.00 | $482.25 | $374.85 |
Gold Price Calculator Implementation
``javascript
function calculateGoldValue(weightGrams, karat, spotPricePerOz) {
const purityMap = {
24: 0.999, 22: 0.917, 18: 0.750, 14: 0.583, 10: 0.417
};
const purity = purityMap[karat] || 0.999;
const gramsPerTroyOz = 31.1035;
const pricePerGram = spotPricePerOz / gramsPerTroyOz;
const pureGoldWeight = weightGrams * purity;
const value = pureGoldWeight * pricePerGram;
return {
weightGrams,
karat,
purity: (purity * 100).toFixed(1) + '%',
pureGoldGrams: pureGoldWeight.toFixed(3),
spotPrice: spotPricePerOz,
value: value.toFixed(2)
};
}
console.log(calculateGoldValue(10, 18, 2000));
// { weightGrams: 10, karat: 18, purity: '75%', pureGoldGrams: '7.5', value: '482.25' }
`
Gold as Investment
Gold serves as inflation hedge and portfolio diversifier. Physical gold (bars, coins) has storage costs. Gold ETFs (GLD) offer easier trading. Spot price is wholesale; retail includes premiums.
The Four Percentage Questions
Almost every percentage problem is one of these, and mixing them up is the most common
arithmetic error there is:
| Question | Formula | Example |
|---|---|---|
| What is X% of Y? | Y × (X ÷ 100) | 15% of 80 = 12 |
| X is what % of Y? | (X ÷ Y) × 100 | 12 is 15% of 80 |
| X is Y% of what? | X ÷ (Y ÷ 100) | 12 is 15% of 80 |
| % change from X to Y | ((Y − X) ÷ X) × 100 | 80 → 92 is +15% |
Percentage Points Are Not Percent
A rate moving from 4% to 5% is one percentage point, and a 25% increase. Both
statements are true and they are not interchangeable — headlines routinely use the smaller
one when reporting a rise and the larger one when reporting a fall.
Increases and Decreases Do Not Cancel
| Start | Change | Result |
|---|---|---|
| 100 | +50%, then −50% | 75 |
| 100 | −50%, then +50% | 75 |
| 100 | −20%, then +25% | 100 |
The reason is that the second percentage applies to a different base. To reverse a −20% you
need +25%, not +20%. This is why a stock that falls 50% must double to break even, and why
"we cut costs 30% then grew 30%" leaves you 9% down.Reversing a Percentage
To find the price before a 20% discount, divide by 0.8 — do not add 20%:
`
before = after ÷ (1 − discount)
$80 ÷ 0.8 = $100 ✓
$80 × 1.2 = $96 ✗
``
The same asymmetry applies to tax, tips, markups and platform fees.