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.