Sandpaper Grit Progression Calculator
Good sanding is about removing each grit's scratches with the next, not jumping straight to fine paper. The common guideline is to step up by no more than about 1.5 times the grit number at a time. This calculator builds the sequence from your start grit to your finish grit using a step ratio you control, reporting how many steps it takes and the number of grits in the sequence. The 1.5 ratio is a rule of thumb, not a physical constant, so it is an editable input you can tune to your abrasives and surface.
Grit progression formula
Next grit = current grit * step ratio (rounded)
Repeat until next grit reaches or exceeds finish grit
Sequence ends on the finish grit
Max next grit from start = start grit * step ratio
Each step multiplies the current grit by the ratio and rounds to a sensible number, then the finish grit is appended so the sequence always ends where you want. The number of steps counts the transitions between grits.
Sanding sequence tips
- Do not jump more than roughly 1.5 times the grit number at once.
- Sand fully at each grit until the previous scratches disappear.
- Pick grit numbers from one consistent scale (CAMI or FEPA P).
- Stop around 180 to 220 for film finishes to keep stain uptake.
- Clean dust between grits so coarse particles do not scratch.
Grit progression: frequently asked questions
How should I step through sanding grits?
A common woodworking guideline is to avoid jumping more than about 1.5 times the grit number at each step, so scratches from the coarser grit are fully removed by the next. This calculator multiplies by your chosen step ratio (default 1.5) from the start grit up to the finish grit and lists the sequence.
Why not skip straight to a fine grit?
Each grit removes the scratch pattern of the previous one. Skipping too far leaves deep scratches that the fine grit cannot erase, so you sand for a long time and still see swirl marks under finish. Stepping in moderate ratios is faster overall because each grit has less work to do.
What is the difference between grit standards?
Sandpaper grit is specified by standards such as the US CAMI scale and the European FEPA P-scale, and the same number can mean a slightly different particle size between them. This calculator works with the grit numbers you supply; pick numbers from one consistent scale and your own abrasive range.
What grit should I finish at?
It depends on the finish. Many woodworkers stop around 180 to 220 grit for film finishes because higher grits can burnish the surface and reduce stain or finish absorption. For bare-wood or oil finishes some go higher. Enter your target finish grit; the calculator builds the steps to reach it.
Does the step ratio have to be exactly 1.5?
No. 1.5 is a widely cited rule of thumb, not a physical constant, which is why it is an editable input. Use a smaller ratio for finer control and faster scratch removal, or a larger ratio to skip more aggressively if your surface allows.
Official sources
- American National Standards Institute: ANSI, coated abrasive grit standards.
- National Institute of Standards and Technology: NIST, particle size metrology.
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.