Rough-to-Cut Yield Estimator
Estimate how many finished carats a piece of rough gemstone is likely to give, the yield percentage, and what each finished carat costs you.
Estimate only, not a guarantee. Budget with the low end of each range. Hidden fractures, colour zoning and the exact cut you request can move the result outside it.
How to Use the Yield Estimator
- Weigh the rough. Enter the weight of the rough in carats or grams.
- Choose the species. Pick the gemstone type. Each species has its own typical yield range.
- Describe the rough shape. Select the shape that best matches the crystal: chunky, prismatic, irregular, water-worn or flat.
- Set the cutting goal and clarity. Choose whether you want maximum weight or a calibrated, high-brilliance cut, and how many inclusions must be cut around.
- Add costs (optional). Enter the rough price per carat and any cutting cost per finished carat to see the break-even cost.
- Read the ranges. Use the finished-weight and yield ranges for planning. Budget with the low end, not the high end.
How the Estimate Is Calculated
Cutting a gemstone always removes material. The estimator starts with the typical weight-retention range for the species you choose, then moves it up or down for the shape of the rough, your cutting goal and how many inclusions must be cut around. Finished weight is simply rough weight multiplied by the yield range.
Example: 10 ct of chunky, clean ruby or sapphire rough cut for maximum weight gives an estimated yield of about 32–40%, or roughly 3.2–4.0 ct finished. 10 ct of irregular, included emerald rough cut with balanced proportions gives about 12–15%, or roughly 1.2–1.5 ct.
Typical Yield Ranges by Gemstone
| Gemstone | Base yield range | Basis |
|---|---|---|
| Ruby / Sapphire (corundum) | 25–40% | Gem-trade reference range |
| Emerald | 15–25% | Gem-trade reference range (fragile, inclusion-rich) |
| Spinel | 20–40% | General coloured-stone range |
| Tourmaline | 20–40% | General coloured-stone range (step cuts can retain more) |
| Aquamarine / Morganite / other beryl | 20–40% | General coloured-stone range |
| Topaz | 30–50% | Gem-trade reference range |
| Quartz / Amethyst / Citrine | 30–50% | Gem-trade reference range |
| Garnet | 20–40% | General coloured-stone range |
| Peridot | 20–40% | General coloured-stone range |
| Tanzanite | 20–40% | General coloured-stone range |
| Other / not sure | 20–40% | General coloured-stone range |
Base ranges are rounded from published faceter guidance (including International Gem Society articles) and gem-trade references. Sources agree that about 20% is a cautious planning figure, about 30% is a good result, and well-shaped rough can exceed 40%.
Adjustments for Shape, Cutting Goal and Clarity
Published guidance says that evenly shaped rough yields more, that cutting to a fixed calibrated size yields less, and that inclusions you must remove lower the result. It does not give exact percentages, so the figures below are our own estimating assumptions. Treat them as a guide, not a measurement.
| Rough shape | Position inside the species range |
|---|---|
| Chunky / well-formed crystal | 45%–100% of the species range |
| Elongated / prismatic crystal | 30%–85% of the species range |
| Irregular or angular fragment | 10%–60% of the species range |
| Water-worn pebble (alluvial) | 15%–65% of the species range |
| Flat / tabular piece | 0%–45% of the species range |
| Cutting goal | Multiplier |
|---|---|
| Maximum weight (free size, native-style cut) | ×1.00 |
| Balanced (good proportions, free size) | ×0.85 |
| Calibrated size / best brilliance | ×0.65 |
| Rough clarity | Multiplier |
|---|---|
| Mostly clean - few inclusions | ×1.00 |
| Some inclusions to cut around | ×0.85 |
| Heavily included or fractured | ×0.65 |
What Affects Rough-to-Cut Yield?
- Crystal shape: blocky, well-formed rough wastes less than flat, thin or heavily projecting pieces.
- Colour orientation: showing the best colour face-up sometimes means cutting in a less economical direction.
- Inclusions and fractures: material that has to be removed to leave a clean stone lowers the final weight.
- Target size and shape: a fixed calibrated size or a demanding outline needs more rough than a free-size cut.
- Cut style: step cuts often keep more weight than brilliant cuts on elongated rough.
Frequently Asked Questions
How much of a rough gemstone is lost when it is cut?
Most of it. Faceters commonly report keeping roughly 20% to 40% of the rough weight, so 60% to 80% is cut away. Around 30% is considered a good result from solid rough, and well-shaped crystals can occasionally exceed 40%.
What is a good yield for rough gemstone?
For planning, many cutters use about 20% as a safe figure and 30% as a good result. Chunky, evenly shaped, clean rough cut for maximum weight sits at the top of the range, while irregular or included rough sits at the bottom.
Why does my cutter result differ from this estimate?
The estimator cannot see your rough. Hidden fractures, colour zoning, the direction chosen to show the best colour, and the exact shape you ask for all change the outcome. Treat the range as a planning guide and ask the cutter for a written estimate after seeing the stone.
Does cutting for brilliance or a calibrated size reduce yield?
Yes. Cutting to fit a fixed calibrated size or to maximise light return usually removes more material than a free-size cut made for weight. Valuable stones are often cut for maximum weight and the setting is made to fit.
How do I convert grams of rough to carats?
One gram equals 5 carats, so 4 g of rough is 20 ct. Choose grams in the estimator and it converts for you.
How do I calculate the cost per finished carat?
Divide the rough price per carat by the yield written as a decimal, then add the cutting cost per finished carat. For example, rough at 100 per carat with a 25% yield costs 400 per finished carat before cutting costs and profit.
Does this estimator work for cabochons?
No. It is built for faceted stones. Cabochons often keep more of the rough weight, but the result depends heavily on the dome height and the rough shape.
Free gemstone buying checklist
12 checks to make before you buy a gemstone online: lab reports, treatments, duties, returns and payment safety. We'll also send occasional gemstone news. Unsubscribe at any time.
We use your email only to send the checklist and occasional updates from AA Gems & Jewelry. No spam. Privacy policy
Looking for natural, certified gemstones?
Shop Natural Gemstones