If you’ve ever stared at a stack of whetstones — a 1,000 here, an 800 there, a 6,000 over here — and wondered whether any of those numbers actually mean the same thing, the answer is no. Grit numbers are not a universal scale. They’re regional standards, measured against different particle distributions, sometimes within the same country. This article translates them.
This is one of the deeper-dive pieces under our Whetstones pillar. Bookmark it; you’ll come back to the conversion table.
What “grit” actually measures
Grit is a particle-size rating. The higher the number, the smaller the abrasive particles, and the finer the resulting scratch pattern. The size is measured in microns (one-thousandth of a millimeter), and that micron rating is the only number that crosses standards reliably. Everything else is conversion math.
Three measurement standards dominate sharpening:
- JIS (Japanese Industrial Standard, R 6001) — used by all Japanese water stones and most “Japanese-style” stones from any country. Defined by particle size distribution as measured by a specific sedimentation test.
- FEPA-F (European, F-grit) — the standard for bonded abrasives in Europe. Used by some European synthetic stones (Naniwa, some King variants, some Sigma).
- ANSI/CAMI (American) — used on US oil stones (Norton India, some Dan’s Whetstone products) and most US sandpaper. Roughly aligned with FEPA at coarse grits, diverging at fine.
A “1,000-grit JIS” stone has particles around 11–14 microns. A “1,000-grit ANSI” stone has particles around 14–16 microns. A “1,000-grit FEPA-F” stone has particles around 10–14 microns. They’re close, but the differences compound dramatically as you go finer.
The conversion table
This is the table you bookmark. Numbers are approximate; actual particle distributions vary by manufacturer.
| Microns | JIS | FEPA-F | ANSI/CAMI | Use case |
|---|---|---|---|---|
| ~76 | 200 | F80 | 80 | Heavy reprofiling, broken edges |
| ~58 | 240 | F100 | 120 | Severe damage, very dull edges |
| ~37 | 400 | F180 | 220 | Coarse — chip removal, reshaping |
| ~20 | 600 | F320 | 320 | Medium-coarse |
| ~14 | 1,000 | F400 | 400–600 | Standard sharpening — most kitchen knives |
| ~9 | 2,000 | F600 | 800 | Mid-grit refinement |
| ~6 | 3,000 | F800 | 1,200 | Fine |
| ~3 | 6,000 | F1200 | 2,000 | Polishing — most users stop here |
| ~1.2 | 8,000 | F1500 | 3,500 | Very fine — razors, mirror polish |
| ~0.5 | 16,000 | — | ~8,000 | Specialist — straight razor finishing |
| ~0.3 | 30,000 | — | ~12,000 | Very specialist — natural stone equivalents |
Practical observation: a 1,000-grit JIS water stone is roughly equivalent to a 600-grit ANSI oil stone in particle size, but the cutting feel is completely different. The water stone’s softer binder breaks down and releases fresh abrasive constantly; the oil stone’s harder binder holds particles longer. Same micron rating, different behavior.
Diamond plates use a different system entirely
Diamond plate makers (DMT, Atoma, Trend) use particle size in microns directly, or they use a separate “extra coarse / coarse / fine / extra fine” labeling system that loosely maps to grit ranges. The key reference points:
| DMT label | Color | Microns | Equivalent (JIS) |
|---|---|---|---|
| Extra Extra Coarse | Black | 120 | ~120 |
| Extra Coarse | Black | 60 | ~220 |
| Coarse | Blue | 45 | ~325 |
| Fine | Red | 25 | ~600 |
| Extra Fine | Green | 9 | ~1,200 |
| Extra Extra Fine | Tan | 3 | ~8,000 |
One quirk worth knowing: a brand-new diamond plate cuts more aggressively than its rated grit suggests. The proudest diamond crystals shear off in the first few sharpening sessions, and the plate settles into its rated cutting behavior. Don’t judge a diamond plate by its first 10 minutes of use.
“Finishing” grits and what they actually do
The marketing fixates on the high-grit end — 8,000, 16,000, 30,000 stones marketed as “razor-sharp finishers.” Three things to keep in mind:
- The sharpest cutting edge isn’t the most polished one. A 4,000-grit edge with a slight tooth can outcut an 8,000-grit polished edge for fibrous food (rope, tomato skins, slicing tasks). The polish reduces draw resistance but also reduces the edge’s grip on slippery surfaces.
- High-grit stones won’t fix a poorly-formed edge. If the apex isn’t even at 1,000 grit, polishing it at 8,000 just gives you a beautifully polished bad edge.
- Diminishing returns are real. The visible difference between a 6,000 and an 8,000 finish is small. Between an 8,000 and a 16,000 it’s smaller. Between a 16,000 and a 30,000 it requires magnification to see.
Stop at 6,000 for kitchen work. Stop at 8,000 for EDC if you want the polish. Go higher only if you’re sharpening straight razors or chasing aesthetics.
Common mistakes when reading grit numbers
- Comparing grit numbers across systems by direct value. A “1,500 grit” sandpaper is not the same as a “1,500 grit” Japanese stone. Always check the standard.
- Assuming higher grit = better. See the previous section. Pick the grit for the job.
- Ignoring the binder. Two 1,000-grit JIS stones from different makers can feel completely different on the steel because the binder hardness varies. The grit number tells you about the abrasive; the binder tells you about how the stone behaves.
- Trusting cheap stones’ grit ratings. Budget stones often have wider particle distributions than premium stones — a “1,000 grit” stone with particles ranging from 5 to 25 microns will feel coarser than a tighter-spec 1,000.
Building a useful progression with the table
The 2x rule is a useful first cut: each stone in your progression should be roughly twice the grit of the previous one. So 220 → 600 → 1,000 → 3,000 → 6,000 — or a tighter 400 → 1,000 → 2,000 → 4,000 → 8,000 — both work. The reason: each stone has to remove the deeper scratches left by the previous one. Skip too much and you spend forever trying to refine a coarse pattern with a fine stone; skip too little and you’ve spent money on stones whose results are indistinguishable from the one before them.
For most users, a three-stone setup is enough: 400, 1,000, and 4,000 (or 6,000). Reprofile or repair on the 400. Sharpen on the 1,000. Refine on the 4,000. Strop afterward if you have one. That’s it.
The quick summary
- Grit numbers only match within the same standard. Always check whether a stone is rated JIS, ANSI, or FEPA.
- The micron rating is the only universal reference. Look it up when in doubt.
- Most kitchen sharpening happens at 1,000–6,000 JIS. Anything below is for damage; anything above is for polish.
- The binder matters as much as the grit. A soft 1,000 cuts faster than a hard 1,000.
- Diamond plates use their own labels. The chart above is the conversion.
Related reading
- The Whetstones Pillar — start here if you’re building your first stone setup.
- Water Stones vs. Oil Stones · coming soon
- The Best Whetstone for Beginners · coming soon
- How to Flatten a Whetstone · coming soon