Build your own painting scenario
One rectangular room, walls only. Enter the coverage on your chosen product’s label and your own rates. Starting values are examples, not a Brisbane price quotation.
Net area = perimeter × height − openings. Paint = net area × coats ÷ coverage, plus waste, rounded up to 0.1 L. Scenario budget = estimated litres × your paint price + your labour hours × your rate. Pack rounding, primer, repairs, access, tax, ceilings and trim are excluded.
Measure the area that receives the coating
For a rectangular room, wall area starts with the perimeter multiplied by wall height. Measure ceilings separately and list doors, frames and other trim as their own items. Decide how openings are treated and use the same method throughout the project. The calculation should explain deductions rather than hide them.
Irregular rooms, raked ceilings, stairwells and exterior elevations may need several smaller measurements. Label each surface so you can update one part without rebuilding the entire estimate. Keep notes about inaccessible areas or dimensions that remain provisional. Precision in the output cannot compensate for an uncertain measurement.
Calculate paint volume before cost
The basic quantity relationship is coated area multiplied by the number of coats, divided by the selected product’s stated coverage per litre. Dulux uses this relationship in its own quantity calculator. Obtain coverage from the current product label or data sheet; do not assume that all primers, wall paints and textured coatings share one spreading rate.
For illustration only, 40 square metres receiving two coats at an entered coverage of 10 square metres per litre produces eight litres before any additional allowance. Those numbers explain arithmetic, not a product recommendation. Actual consumption, pack sizes and material left for maintenance may change the amount purchased.
Add transparent project allowances
If you want a cost scenario, enter prices or labour allowances obtained for your own project. Keep paint, preparation materials, tools, equipment, labour and other expenses separate. Show whether tax is included. This makes it possible to change one assumption and see its effect without implying that the result is a live industry tariff.
Preparation should have its own description. Cleaning a sound wall, repairing damage and dealing with an unknown existing coating are not interchangeable tasks. Likewise, access equipment or occupied-room protection may require a separate allowance. Mark missing information as unresolved instead of silently entering zero.
- Separate wall, ceiling, trim and preparation products.
- Enter coat counts for each product rather than one global total.
- Keep optional work visible in a separate scenario.
Use scenarios to ask better questions
Compare a base scope with an expanded scope, such as adding ceilings or including another room. Keep the original assumptions alongside the result so the difference is understandable. A useful calculator report should be reproducible from the saved measurements and inputs.
Before buying materials or accepting a contract, confirm the actual coating system, preparation and site conditions. The greatest value of a preliminary estimate is often the list of questions it exposes. It gives you a structured brief to discuss, rather than a precise-looking total without a defined scope.
Questions, clearly answered
Why might purchased paint exceed the calculated volume?
The calculation may not account for every surface condition, application loss, pack size or maintenance allowance. Check the product guidance and explain any additional allowance instead of presenting the theoretical volume as a guaranteed purchase quantity.
Can the result replace an on-site assessment?
No. Measurements and entered costs do not establish substrate condition, access requirements or the appropriate preparation. A final project scope needs those conditions to be assessed separately.