Grit Size to Micron Chart
Quick answer: grit labels do not have one universal micron conversion. This chart is a selected diamond-abrasive reference for lapidary polishing: 8,000 grit is about 3 microns, 14,000 grit about 1 micron, and 100,000 grit about 0.25 micron. Check the abrasive maker’s grade and particle-size specification before treating two products as equivalents.
Diamond Grit to Micron Chart
The values below describe selected diamond-abrasive grades used in lapidary work. The particle-size range and the approximate grade value are reference figures, not guaranteed limits for every product.
| 100,000 | 0-0.5 | 0.25 | Ultra-fine specialty polish |
|---|---|---|---|
| 60,000 | 0-1 | 0.5 | Very fine polishing |
| 14,000 | 0-2 | 1 | Fine commercial polish range |
| 13,000 | 1-2 | 1.5 | Fine polish range |
| 9,000 | 2-3 | 2.5 | Fine pre-polish/polish range |
| 8,000 | 2-4 | 3 | Common pre-polish range |
| 5,000 | 2-6 | 4 | Fine abrasive |
| 4,500 | 4-6 | 5 | Fine abrasive |
| 2,800 | 5-10 | 7 | Pre-polish range |
| 1,800 | 6-12 | 9 | Fine sanding/lapping |
| 1,400 | 8-20 | 14 | Fine sanding/lapping |
| 1,200 | 10-20 | 15 | Fine sanding |
| 1,050 | 12-25 | 18 | Fine sanding |
| 800 | 20-30 | 25 | Fine finishing |
| 600 | 20-40 | 30 | Common finishing grit |
| 500 | 30-40 | 35 | Finishing grit |
| 325 | 40-50 | 45 | Coarser finishing/lapping |
| 240 | 60-80 | 70 | Coarser sanding |
| 160 | 100-120 | 110 | Coarse sanding |
| 100 | 120-160 | 150 | Coarse sanding |
20 rows
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How to Compare Abrasive Grades
A micron is one-thousandth of a millimeter. A smaller particle-size value generally indicates a finer abrasive. Grit numbers, however, depend on the abrasive type and grading system. Diamond powder grades should not be assumed to match sandpaper grit, FEPA P/F grades, or mesh numbers one-for-one.
- Confirm that both products use the same abrasive and grading convention.
- Use the manufacturer’s stated particle-size range when a finish or process depends on it.
- Move through intermediate grades when polishing; a large jump can leave scratches that finer powder will not quickly remove.
- Follow the lap, compound, and workpiece manufacturer’s instructions for application and cleanup.
Grit, Micron, and Mesh Are Different Labels
Microns describe particle dimensions. Mesh describes a sieve or screen classification and is most useful for coarser particles. Grit is a grade designation whose meaning varies by system. Fine polishing powders are classified by particle-size methods rather than by passing through a practical mesh screen, so a single mesh conversion does not apply across this chart.
Sources
The selected diamond-powder values are compared with the Faceting Museum diamond conversion chart. FEPA’s grain standards overview explains that abrasive grades are defined by different standards and particle-size distributions.
