Gemstone Price Per Carat Calculator
Calculate gemstone price per carat and total cost by quality grade.
Returns retail, wholesale, and resale estimates for diamonds, rubies, and sapphires.
Gemstone pricing follows a unique pattern: the price per carat increases exponentially with size, not linearly. This is because larger stones of good quality are exponentially rarer than smaller ones.
Basic Price Formula
Total Price = Price Per Carat × Carat Weight
But the per-carat price itself depends on size. This relationship is often expressed as:
Price Per Carat = Base Price × (Weight)^n
Where n is typically 1.5–2.0 for precious stones, meaning a 2-carat stone costs significantly more than twice the price of a 1-carat stone.
Price Per Carat Reference (approximate retail USD, 2024)
| Gemstone | Low Quality | Medium Quality | High Quality | Exceptional |
|---|---|---|---|---|
| Diamond (1 ct) | $2,000 | $5,000 | $12,000 | $25,000+ |
| Ruby (1 ct) | $500 | $2,500 | $8,000 | $20,000+ |
| Sapphire (1 ct) | $400 | $1,500 | $5,000 | $15,000+ |
| Emerald (1 ct) | $300 | $1,500 | $5,000 | $12,000+ |
| Tanzanite (1 ct) | $100 | $400 | $800 | $1,200 |
| Aquamarine (1 ct) | $50 | $200 | $500 | $1,000 |
| Amethyst (1 ct) | $5 | $15 | $30 | $50 |
| Garnet (1 ct) | $10 | $50 | $200 | $500 |
| Opal (1 ct) | $20 | $100 | $500 | $3,000+ |
| Tourmaline (1 ct) | $50 | $200 | $500 | $2,000+ |
Size Premium Factor
Prices per carat jump at key weight thresholds:
- Under 0.5 ct: Base price
- 0.5–1.0 ct: 1.5–2× base
- 1.0–2.0 ct: 2–4× base
- 2.0–3.0 ct: 4–8× base
- 3.0–5.0 ct: 8–15× base
- Over 5 ct: 15–30× base (for precious stones)
Worked Example
A 1.8 carat medium-quality sapphire:
- Base per-carat (medium): $1,500
- Size premium for 1–2 ct range: ~3× for sapphire
- Adjusted per-carat: $1,500 × 3 = $4,500
- Total: 1.8 × $4,500 = $8,100
The “Four Cs” (Cut, Color, Clarity, Carat) apply primarily to diamonds but similar quality factors affect all gemstones. Origin also matters significantly — Burmese rubies, Kashmir sapphires, and Colombian emeralds command premium prices over similar-quality stones from other sources.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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