How much sugar soap do I need?

Sugar soap concentrate is used at approximately 0.05 L/m² when diluted according to the packet instructions. A 1L bottle of concentrate is enough for roughly 20 m² of wall area. For heavily soiled or greasy walls (kitchens), you may need double this. Sugar soap removes dirt, grease, and old paint residue to ensure good adhesion of new paint.

How much filler do I need for my walls?

The amount depends on wall condition. Good condition walls need about 0.02 kg/m² (just nail holes). Fair condition with some cracks needs 0.08 kg/m². Poor condition with extensive cracking needs 0.20 kg/m² or more. A standard 1 kg tub of filler covers 5-50 m² depending on condition. Use fine surface filler for small imperfections and deep fill for holes over 5mm.

How far does a caulk cartridge go?

A standard 310ml cartridge of decorator's caulk covers approximately 12 linear metres with a 5mm bead. For wider gaps (up to 10mm), coverage drops to about 6 metres per cartridge. Use decorator's caulk (not silicone) for gaps between walls and woodwork — it's paintable and flexible. Apply with a caulk gun and smooth with a wet finger for a neat finish.

What grit sandpaper should I use for decorating?

Use 80 grit for heavy sanding and paint removal. Use 120 grit for general smoothing of filler and between coats. Use 240 grit for fine finishing between topcoats. Each sheet of 120 grit covers roughly 2 m² before it wears out. For large areas, a sanding pole or orbital sander saves significant time. Always sand in the direction of the wood grain on timber.

Do I need to sand between coats of paint?

Light sanding between coats with 240 grit gives a smoother finish, especially for gloss and satin finishes. It removes dust nibs and provides a key for the next coat. For matt emulsion on walls, sanding between coats is usually unnecessary unless there are visible imperfections. For best results on woodwork, lightly sand and wipe with a tack cloth between every coat.

TradeCalculator

Decorator's Prep Calculator — Sugar Soap, Filler, Caulk & Sandpaper

Calculate all preparation materials for decorating: sugar soap, filler by wall condition, caulk cartridges, sandpaper sheets, and masking tape.

Wall Area

Total wall area to prep

Ceiling Area

Ceiling area (for sugar soap)

Wall Condition

Determines filler quantity

Caulk Length

Gaps between walls and woodwork

Window/Door Perimeter

For masking tape estimate

How We Calculate This

This calculator estimates all preparation materials needed before painting. The main variable is wall condition — poor condition walls need significantly more filler and sanding time.

The formula

Sugar soap (L) = Total area × 0.05 L/m² × Wastage

Filler (kg) = Wall area × Rate by condition × Wastage

Caulk cartridges = Linear metres ÷ 12 m per cartridge

Sandpaper sheets = Wall area ÷ 2 m² per sheet

For example, a room with 40 m² walls and 12 m² ceiling in fair condition: Sugar soap = 52 × 0.05 = 2.6 L (3 bottles). Filler = 40 × 0.08 = 3.2 kg (4 tubs). Sandpaper = 40 ÷ 2 = 20 sheets.

Filler rates by condition

Good: 0.02 kg/m² — a few nail holes only
Fair: 0.08 kg/m² — some cracks and dents
Poor: 0.20 kg/m² — extensive cracking and damage

Frequently Asked Questions

Related Calculators

Paint Coverage Calculator

Calculate how many litres of paint you need for walls and ceilings.

Wallpaper Calculator

Work out how many rolls of wallpaper you need for any room.

Primer Coverage Calculator

Calculate primer quantities for walls, wood and metalwork.

Wood Stain Calculator

Calculate wood stain or varnish needed for decking, fences and furniture.

Masonry Paint Calculator

Calculate exterior masonry paint for outside walls.

Last updated: March 2026

All calculations are estimates. Verify with your supplier.