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400grit sandpaper

Extra Fine

Wet sanding clear coat. Plastic finishing.

400 grit in other scales

If the pack says 400 (CAMI, most US paper)

~23 µmAbout the same as P800.

If it says P400 (FEPA, Festool, Mirka, Norton 3X)

~35 µmAbout the same as CAMI 320.P400, converted →

Sizes are average particle diameters from the published CAMI and FEPA tables. Full ladder in the grit chart; any grade on any scale in the grit converter.

What 400 grit is for

400-grit is where wet sanding starts to dominate. It’s standard for color-coat prep on auto-body, between-coat sanding on clear finishes, and the first refinement step on metal heading toward polish.

Projects at 400 grit

  • · Wet sanding auto color coat before clear
  • · Between-coat sanding on instrument lacquer
  • · First metal-finishing pass after coarse shaping
  • · Smoothing fiberglass and composite repairs
  • · Pre-polish on stainless steel

Abrasive materials

  • · silicon carbide (default for wet sanding)
  • · aluminum oxide (dry)
  • · ceramic

Common mistake

On clear coat, 400 is too aggressive for finish wet sanding: drop to 1000+ once the orange peel is leveled.

← 320 grit (the step before)600 grit (the step after) →

Top pick at 400

Mirka Gold 5-inch Hook & Loop Disc Assortment

Clicks in smooth. Finnish-made. Doesn't ask you to stop.

Check priceReview

Catalog fit

13

Current SKU matches in this grit lane.

Common forms

2

Forms represented here, led by discs.

Head to head

2

Comparison pages currently touching this stage of the sanding climb.

Use this grit when

The surface still needs this stage.

  • · Wet sanding clear coat. Plastic finishing.
  • · This is refinement territory. It improves the surface that is already close rather than rescuing a rough one.
  • · On this site, 400 grit shows up most around 6-inch orbital sanders, Festool sanders, fine finishing, and fine furniture.

Skip this grit when

The job is earlier or later than this.

  • · Skip this grit if the surface still has deep scratches, filler ridges, or obvious machine marks from coarse paper.
  • · Skip it unless the abrasive itself is labeled for wet use when you plan to add water.

Recommended at this grit.

Head to head

Comparisons in this lane.

Mirka Gold 5-inch Hook & Loop Disc Assortment vs. Diablo 5-inch ROS Discs, 120 Grit (50-pack)

Finnish precision or American volume.

Read the breakdown →

Mirka Gold 5-inch Hook & Loop Disc Assortment vs. 5-Inch Random Orbital Sander + Disc Starter Bundle

You either have the sander or you don't.

Read the breakdown →

Questions people ask

The practical part.

What is 400 grit actually for?

400 grit is for wet sanding clear coat. plastic finishing. This is refinement territory. It improves the surface that is already close rather than rescuing a rough one.

What should come before and after 400 grit?

The safe lane is usually 320 -> 400 -> 600. You can stretch that a little on easy material, but large jumps usually leave scratches behind.

Which forms make the most sense at 400 grit?

On UltraRough, this grit shows up most in discs and sheets. That reflects where shoppers usually need this cut level in the real world.

Keep moving

Follow the climb.

320 gritThe step before 400 grit.600 gritThe next step after 400 grit.DiscsSee discs that commonly show up in this lane.SheetsSee sheets that commonly show up in this lane.Use the grit selectorStart from the project instead of the number.Read the full grit chartSee the entire progression from coarse to mirror.Sandpaper grit chart: coarse to fineThe full range mapped to projects — every grit from 40 to 3000.Find the right grit for your projectTell us the job; we'll tell you where to start and where to stop.
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