Why US Gold Weighing Uses Three Different Units
If you've ever had gold weighed at a jeweler, pawn shop or refiner in the US, you've probably seen the result quoted in a unit you don't use anywhere else: pennyweight, or "dwt." It's a holdover from historical coin weighing, and it's still the everyday unit much of the US precious metals trade uses on the scale — alongside grams (the international standard) and troy ounces (the unit gold itself is priced in on commodity markets). None of these are interchangeable with the "ounce" on your kitchen scale — that's an avoirdupois ounce (28.3495 g), a different measurement entirely from a troy ounce (31.1034768 g).
This calculator accepts all three so you can enter whatever your scale or your jeweler's receipt actually shows, without doing the conversion math by hand first.
Karat Stamps: What to Look For
Before weighing, find the karat stamp — usually a tiny mark inside a ring band, on a clasp, or on the inner surface of a bracelet. US jewelry is regulated under the FTC's Jewelry Guides (16 CFR Part 23), which require a karat quality mark plus a registered trademark identifying who stands behind it — the FTC's own consumer guide, Buying Platinum, Gold, and Silver Jewelry, recommends not trusting a karat mark that appears without a nearby trademark.
| Stamp | Fine gold content | Typical use |
|---|---|---|
| 24K | 99.9% | Bullion, coins — too soft for everyday jewelry |
| 22K | 91.7% | South Asian / Middle Eastern-American bridal jewelry |
| 18K | 75.0% | Fine jewelry, engagement rings |
| 14K | 58.5% | Most common US everyday jewelry |
| 10K | 41.7% | Lowest karat still legally sold as "gold" in most states |
How This Calculator Works — Formula & Method
Source: live per-gram feed from usgoldpricepergram.com · deterministic calculation — no AI, no arbitrary estimate
Unit conversion constants
| Unit | Grams | Source |
|---|---|---|
| 1 pennyweight (dwt) | 1.55517384 g | Standard troy weight system |
| 1 troy ounce (oz t) | 31.1034768 g | Standard troy weight system |
Melt value formula
grams = amount × (unit === 'dwt' ? 1.55517384 : unit === 'ozt' ? 31.1034768 : 1)
— apply karat price —
melt_value_usd = grams × price_per_gram(karat)
— price source —
price_per_gram(karat) ← live fetch from usgoldpricepergram.com/gold-data.json
This is an estimate of raw gold content value, not a buyer's offer — actual cash-for-gold offers are lower to cover refining and margin.
🥇 Want Today's Exact Price by Karat, Not Just an Estimate?
This calculator gives you a melt value estimate for one item at a time. But gold prices move throughout the trading day, and if you're actually deciding when to sell — or comparing offers from more than one buyer — you need the live per-gram rate in front of you, updated automatically rather than typed in by hand. That's exactly what usgoldpricepergram.com is built for: a dedicated live gold price tracker for the US market, broken out by karat.
A few concrete ways people use it alongside a melt value calculator like this one:
- Before calling a buyer: check the live 14K or 10K price per gram first, so you know roughly what to expect instead of walking in blind.
- Comparing multiple offers: get a quote from one pawn shop, then check the live spot rate to see how big a discount they're actually applying.
- Selling in bulk by karat: the site's dedicated 24K, 22K, 18K, 14K and 10K pages let you price each karat separately instead of guessing with one blended number.
- Tracking a decision over days: since the price updates three times daily, you can watch it move before deciding when to sell rather than acting on a single snapshot.
- Checking the cash-for-gold gap: the site's dedicated cash-for-gold page shows an estimated buyer discount on top of the live spot rate, similar to what this calculator does for melt value.