Wall filler calculator
Patching a wall before painting takes little filler — the question is usually whether a small tub is enough. The calculator estimates it from the number of small and large holes.
Your measurements
Result
- Filler needed
- 0.15 kg
For cracks wider than 5 mm or structural cracks, embed a reinforcing mesh before filling.
How the calculation works
- Filler (kg) = small holes × about 10 g + large holes or cracks × about 50 g.
Worked example
For 5 small plug holes and 2 larger holes: 5 × 0.01 + 2 × 0.05 = 0.15 kg — a small tub of filler is enough.
What the calculator assumes
- Small holes are under 2 cm (wall plugs, nails); large ones are 2–5 cm or short cracks.
- Filler goes on in 1–2 coats and is sanded before painting.
When to adjust the result
- Holes larger than about 5 cm in plasterboard are repaired with a board patch, not filler alone.
- Cracks that keep coming back or go through the wall may have a structural cause — have them checked first.
Filling holes and cracks that do not reappear
Match the filler to the job: ready-mixed lightweight filler for small holes, powder filler for deeper repairs, flexible filler for cracks that move with the seasons. Deep holes are filled in layers of a few millimetres each, letting each one dry, so the filler does not shrink or sag.
Open fine cracks slightly with a scraper so filler can get in, dampen or prime dusty surfaces, and overfill a little before sanding flush. Cracks that keep reopening, run diagonally from doors and windows or are wider than a few millimetres may point to movement in the building rather than a cosmetic problem.
Frequently asked questions
How do I fill a large hole in plasterboard?
Cut a clean square, fit a patch of board on a backing piece, then tape and fill the joints.
Why does filler crack?
Usually because a deep hole was filled in one thick layer — fill deep holes in several thin layers.
Why does filler crack or sink?
Usually too thick a layer at once, or a crack that is still moving. Fill deep holes in stages and use flexible filler on moving cracks.
Do I need to prime filler before painting?
Yes — filled patches absorb paint differently and show through as dull spots unless primed or spot-painted first.