PAINT · 5 MIN READ
How much paint does your room need?
A paint estimate combines wall area, openings, coats and the coverage on the can. Keeping those inputs separate makes it easier to see why your required quantity changes.
Find the surface you are painting
For all four walls of a rectangular room, calculate 2 × (length + width) × height. Subtract the measured area of doors and windows. If you will paint the ceiling with the same paint, include ceiling area using the checkbox.
In the planner, assign Paint only to the walls you intend to paint. A wall assigned Wallpaper is excluded from the paint total. Included lower panel zones are also deducted; paint to finish the panels is a separate cost.
Worked example: net wall area
A 16 × 12 ft room with an 8 ft ceiling has 448 sq ft of gross wall area. Subtract one 21 sq ft door and two 12 sq ft windows: 448 − 21 − 24 = 403 sq ft.
Multiply by coats before dividing by coverage
Use the coverage per gallon per coat printed on the actual product. Coverage can depend on surface preparation, texture, application method and the paint itself. The example setting of 350 sq ft is editable.
The formula is surface area × coats × (1 + extra allowance), divided by coverage per gallon. The result is rounded up to whole one-gallon cans.
Worked example: two coats
403 sq ft × 2 coats × 1.10 = 886.6 sq ft of adjusted coverage. At an example 350 sq ft per gallon per coat, that is about 2.53 gallons, rounded up to 3 one-gallon cans. At an example $42 per can, materials cost $126.
Keep primer and trim separate
This calculation does not include primer, trim paint, rollers, brushes, protection sheets or preparation. A change from a dark finish to a light one may change the product or coating system you need; follow the product instructions.
Including the ceiling assumes the same product, coverage and number of coats. The ceiling uses the default wall color. Create a separate project if it needs a different paint specification.
Assign only the walls you will paint
Choose Paint as the finish for each painted wall. The calculator deducts positioned openings and any included lower panel zone from those walls only. Wallpaper walls are excluded. Paint for the panels themselves is a separate finishing cost, not silently included.
Use the 2D elevation to check every opening. The worked whole-room example assumes all four walls are assigned to paint and no panel zones are included.
Treat the preview color as an idea
Use palettes, hex codes and RGB controls to compare the feel of a wall. Each wall can use a different color; the shopping list rounds whole cans separately for each color. They are not manufacturer color matches and will look different across screens and lighting conditions. Test a physical sample in your room.
Enter your quote for paint and labor and wait for All changes saved. Painting labor is charged against the paintable surface area in the planner, not multiplied by the number of coats; use an all-coats labor rate if entering a per-area quote.
Written for Roomplanza to explain this website’s planning and calculation methods. Numerical prices and allowances are illustrative. Verify product specifications with your supplier. Read our methodology and limitations.