Sanding a coat that has not cured — it tears and loads the paper Cutting through on edges, which shows as a pale line under gloss Skipping the dust removal, which is most of the point of the exercise

Which sandpaper grit between coats of paint or varnish?

220 to 320 grit with almost no pressure — you are knocking off dust nibs, not removing the coat.

Sanding between coats does two jobs: it removes the dust nibs and raised fibres that spoil the next coat, and it gives a mechanical key so the coats bond. Neither needs much material removed, and the classic mistake is cutting through on edges and mouldings, where the film is thinnest, and exposing the primer or bare wood underneath. Timing matters as much as grit — a coat sanded before it has cured tears and rolls rather than cutting, and it clogs the paper immediately. Between coats of water-based paint the surface is often ready in hours but the film keeps hardening for weeks, so light pressure is the safeguard. Remove the dust with a vacuum and a tack cloth, since anything left becomes part of the finish.

The options, ranked

Ranked best-first for the stated job. The third column is why the others exist.
Option	Good at	Bad at
240-320 grit	Removes nibs and brush marks and leaves a key without cutting through to the layer below.	Loads quickly on a coat that has not cured properly.
Stearated (non-loading) paper	A soap-like coating stops paint balling up on the abrasive, which doubles or trebles its useful life.	The stearate can interfere with some water-based topcoats and lacquers — check the finish maker's advice.
Abrasive pad or fine nylon web	Follows mouldings and curves where paper cannot, and will not cut through an edge.	Less aggressive, so it takes longer on a genuinely rough coat.
400 grit wet	A very fine cut for high-gloss work where the surface must be flat as well as smooth.	Needs a fully cured film, or the paper drags and tears the coating.

Technique that changes the outcome

Wait for the recoat time on the tin, and longer in cold or humid conditions
Use fingertip pressure only, and keep off arrises and edges
Vacuum, then wipe with a tack cloth or a barely damp lint-free rag
On mouldings use a pad rather than paper wrapped round a finger

What goes wrong

Sanding a coat that has not cured — it tears and loads the paper
Cutting through on edges, which shows as a pale line under gloss
Skipping the dust removal, which is most of the point of the exercise

Compiled practical guidance rather than a published standard. Product formulations vary by brand and market, so read the label — and where the work is structural, electrical or gas, the regulations that apply where you are govern rather than anything here.

For	Use
Bare wood	80 to 120 to 150 on softwood, finishing at 180 or 220 on hardwood — and stop there, because over-sanding ruins stain.
Stripping paint	40 to 80 grit open-coat aluminium oxide or ceramic — but test for lead paint before sanding anything painted before the 1990s.
Rusty metal	60 to 80 grit to strip scale, 120 to 180 to blend — then prime the same day, because bare steel flash rusts within hours.
Plasterboard filler	120 to 150 grit to level joint compound and 220 for the final pass, ideally on a mesh with a vacuum attached.
Plastic	Start at 320-600 wet for scratches, work up to 2000, then finish with a plastic polish — and keep it cool.
Car body filler	80 grit to shape, 180 to refine, 320 before primer and 400-600 on the primer before paint.
Final finish	400 to 600 dry, or 800 to 2000 wet on a fully cured film, followed by a polishing compound.
Wet sanding	Silicon carbide wet-or-dry paper, water with a drop of detergent, a rigid block, and 800 grit upwards.

Common questions

Which sandpaper grit between coats of paint or varnish?: 220 to 320 grit with almost no pressure — you are knocking off dust nibs, not removing the coat.
What should I avoid?: Sanding a coat that has not cured — it tears and loads the paper Cutting through on edges, which shows as a pale line under gloss Skipping the dust removal, which is most of the point of the exercise

Which sandpaper grit for bare wood before finishing? 80 to 120 to 150 on softwood, finishing at 180 or 220 on hardwood — and stop there, because over-sanding ruins stain.
Which sandpaper grit removes paint? 40 to 80 grit open-coat aluminium oxide or ceramic — but test for lead paint before sanding anything painted before the 1990s.
Which sandpaper grit removes rust? 60 to 80 grit to strip scale, 120 to 180 to blend — then prime the same day, because bare steel flash rusts within hours.
Which sandpaper grit for plasterboard and filler? 120 to 150 grit to level joint compound and 220 for the final pass, ideally on a mesh with a vacuum attached.
Which sandpaper grit for plastic? Start at 320-600 wet for scratches, work up to 2000, then finish with a plastic polish — and keep it cool.
Which sandpaper grit for car body filler? 80 grit to shape, 180 to refine, 320 before primer and 400-600 on the primer before paint.
Which sandpaper grit for a final finish? 400 to 600 dry, or 800 to 2000 wet on a fully cured film, followed by a polishing compound.
Which sandpaper should I use for wet sanding? Silicon carbide wet-or-dry paper, water with a drop of detergent, a rigid block, and 800 grit upwards.

Sources

Typical range compiled from manufacturer specifications — At One Place

How these figures are compiled and checked