Understanding your result
The headline is the working hours, with the passes, belts or discs, edger discs and days beside it. The table lists the abrasive for each grit, the totals, the dust bags and the time split into sanding and edging, vacuuming between passes, total hours and elapsed time for the number of people working.
The floor is divided into two areas. The field is what the big machine covers; the edge strip is the band about 6 in wide along every wall that only the edger reaches. The edger is slow and hard work, and on a room with many walls and doorways it takes nearly as long as the field, which is why the wall length is an input. Abrasives are counted per grit for each machine because rental shops sell them that way and because the coarse grits wear out faster.
Working hours are the sanding and edging passes plus vacuuming between grits. Vacuuming is not optional: a stray grain of 36 grit dragged by a 100 grit belt leaves a scratch that shows under the finish. Days assume 8 hours on the machines. For the floor’s installed cost compared with doing it yourself, the DIY vs pro calculator takes these hours, and the installation time calculator plans the whole job including the finish coats and their drying times.
How we calculate this
The abrasive life and production rates are planning figures from abrasive makers’ guidance and installer rules of thumb, not standards, and real life varies with the species, the old finish and how hard the machine is pushed. Old finish loads coarse belts quickly, which is why their life is lower. The grit sequences follow the rule of never skipping more than one grit. The guide to refinishing a hardwood floor explains each pass, the finish choices and the drying times; the finish itself is measured in gallons, which the hardwood floor finish calculator on our sister site Paints Calculator works out from the same area at Paints Calculator.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Grit sequences | 36-60-80-100 (full), 24 start (heavy), 60-80-100 (new), 120 screen | Common practice in NWFA sanding training and abrasive makers’ guidance; never skip more than one grit |
| Belt life, drum sander | 200 / 250 / 300 sq ft per belt | Planning figures from abrasive suppliers’ estimating guidance; old finish loads coarse belts fastest |
| Disc life, orbital sander | 80 / 100 / 125 sq ft per disc | Orbital machines use two to three times the abrasive of a drum |
| Edger | 6 in strip along the walls, 40 sq ft per 7 in disc, 60 ft per hour per pass | Installer rules of thumb |
| Production | 200 sq ft per hour per pass (drum), 120 (orbital) | Amateur with rented equipment, including moving the machine; professionals are faster |
| Vacuuming | 1 hour per 1,000 sq ft per pass | Rule of thumb |
Assumptions last reviewed October 8, 2026.
The calculator does not count the finish, the stain, the wood filler or the plastic sheeting to contain the dust, and it does not know the wear layer of an engineered floor, which decides whether you can sand at all. It assumes a sound, flat floor; a floor with cupped boards needs the drum run diagonally first, which adds a pass. For whether the floor is solid or engineered and how much wood is left, see the guide to solid, engineered and laminate floors. For the cost of having a professional do it, the guide to what installers charge has the ranges.
Two worked examples
A full refinish of 550 sq ft with a drum sander
110 ft of wall, a sound floor with old finish (36, 60, 80, 100), one person.
- Edge strip: 110 × 0.5 = 55 sq ft; field 495 sq ft
- Belts: 3 at 36 grit, 2 each at 60, 80 and 100 = 9 belts; edger discs 2 per grit = 8
- Sanding: 495 ÷ 200 × 4 = 9 h 54 min; edging 110 ÷ 60 × 4 = 7 h 20 min
- Vacuuming: 0.55 × 4 = 2 h 12 min
- Total: 19 h 26 min, three days on the machines, plus 8 dust bags
Three days of rental before any finish goes down. The edger takes almost as long as the drum, which surprises everyone; a room with built-ins, radiators and many doorways can take longer at the edges than in the field.
A screen and recoat of a 180 sq ft bedroom with an orbital sander
56 ft of wall, intact finish, one 120 grit pass.
- Edge strip: 28 sq ft; field 152 sq ft
- Abrasive: 2 orbital discs and 1 edger disc
- Sanding 1 h 16 min, edging 56 min, vacuuming 11 min
- Total: 2 h 23 min
A screen and recoat is an afternoon’s work and a fraction of the cost of a full refinish. It works only because the old finish is intact; one worn-through traffic lane turns it into the full job.
Where to find your inputs
Floor area. Wall to wall, including closets. The floor area calculator adds up odd rooms.
Wall length. The perimeter of every room sanded, including closets, with doorways left in: the edger runs past them too. The perimeter calculator gives it.
Condition. Intact finish and no bare wood: screen and recoat. Worn or scratched finish on a flat floor: full refinish. Thick old finish, paint, cupping or deep gouges: heavy. Unfinished new boards: the new-floor sequence.
Sander. What the rental shop has. Most have both; the drum is faster, the orbital safer.
Common mistakes
- Skipping grits. Going from 36 straight to 100 leaves the 36 grit scratches under the finish.
- Stopping the drum while it runs. It gouges a hollow in seconds. Lift the drum before stopping.
- Forgetting the edges. The edger is half the job on a room with many walls.
- Not vacuuming between grits. A loose coarse grain scratches the finer pass.
- Sanding engineered flooring blind. Check the wear layer at a floor vent or threshold first.
- Leaving dust bags full indoors. Sanding dust with finish residue can self-ignite. Empty bags outdoors into a metal can.
Questions people ask
- How many sanding belts do I need for a floor?
- Roughly one belt per 200 sq ft of field for coarse grits and one per 250 to 300 sq ft for the finer grits, per pass. A 550 sq ft floor sanded at 36, 60, 80 and 100 grit needs about 9 belts plus 2 edger discs per grit. Rental shops usually take back unopened abrasives, so buy one extra of the coarsest grit.
- What grit sequence should I use to refinish a hardwood floor?
- For a sound floor with old finish, 36, 60, 80 and 100. For heavy finish, cupping or deep scratches, start at 24. For a new unfinished floor, 60, 80 and 100. Never skip more than one grit between passes, or the scratches of the coarser grit show under the finish.
- How long does it take to sand a hardwood floor?
- For a competent amateur with a rented drum sander, about 4 to 5 hours of work per 100 sq ft across all passes, edging and vacuuming included. A 550 sq ft floor is about 19 hours, so three working days before finishing starts. A professional crew is two to three times faster.
- Drum sander or orbital sander?
- A drum or belt sander removes finish fast and is the professional choice, but it gouges the floor if it stops while running. A random orbital floor sander cannot gouge and is easier for a first-timer, but it is slower and uses two to three times the abrasive. For a heavy job, the drum is the realistic option.
- What is a screen and recoat?
- A light abrasion of the existing finish with a 120 grit screen, followed by a fresh coat of finish. It does not reach bare wood, takes a few hours, and only works on a floor whose finish is intact and not waxed. It is the right job for a dull floor with no damage.
- How many times can a hardwood floor be sanded?
- Solid 3/4 inch flooring has about 1/4 inch of wood above the tongue and can be fully sanded perhaps five to seven times. Engineered flooring with a 2 mm wear layer can be sanded once, carefully, or only screened; a thinner wear layer cannot be sanded at all. Check the wear layer before you rent a drum.