Painting & decorating
Separate wall paint from ceiling paint before ordering
Measure the surfaces independently so coverage and container rounding stay tied to the right product.
A room's floor area is not its wall area. Measure the room geometry first, then separate surfaces by product, colour and coating system. This avoids combining quantities that cannot share a container.
Work through one room
An illustrative 5 m × 4 m room with 2.7 m-high walls has 2 × (5 + 4) × 2.7 = 48.6 m² of gross wall area. Deducting a 1.89 m² door and a 2.4 m² window leaves 44.31 m² of flat wall face. The ceiling remains 20 m². Reveals, trims and doors need their own measurement lines if included.
Apply coats and coverage once
At an illustrative 10 m²/L per coat, two wall coats require 44.31 × 2 ÷ 10 = 8.862 L before allowance. The ceiling at that same example rate requires 4 L. Replace the rate and coat count with the selected product's instructions for the actual surface.
Keep separate purchase lines
A wall colour and a ceiling finish should be rounded into their own container quantities. If two rooms genuinely share the same product and colour, combining their requirements before rounding may avoid unnecessary containers.
Review the measured scope
The Nowra case study follows this separation using its own recorded dimensions. It does not establish your room's coverage or actual consumption. Check the substrate and preparation requirements, and retain a note of what the opening deductions excluded.
Further reference
The worked numbers in this guide are illustrative unless a project record is identified.
Found a measurement or calculation issue? Send the example and your correction.