Separate wall and ceiling estimates

Paint Calculator

Estimate paint for a rectangular room, subtract doors and windows, and choose coverage and coats for each surface.

Room and paint details

Choose how many length-side and width-side walls you are painting. Count openings only in those walls. Opening dimensions are averages per door/window; for differing sizes use an average with the same total area. No ceiling openings are deducted.

Override the example 350 ft²/US gallon coverage with your paint manufacturer's rate. Surface choices are planning assumptions: textured reduces coverage by 15%, porous by 30%. If your entered coverage already accounts for the actual surface, choose Smooth / sealed to avoid reducing it twice. Primer, trim, doors and window frames are not included as painted surfaces.

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How much paint do I need?

Gross wall area = (length × length-side wall count + width × width-side wall count) × height. Net wall area subtracts door and window count × width × height. Ceiling area = length × width when included. Deductions larger than the selected walls are rejected rather than silently hidden.

Gallons = net area × coats × (1 + waste / 100) / effective coverage. Effective coverage equals the entered rate multiplied by the selected surface factor (1.0, 0.85 or 0.70). Each surface has its own coats and coverage. Needed volume is shown in US gallons and quarts; purchasing rounds upward to the next quarter gallon separately for walls and ceilings.

This is a rectangular-room planning estimate. Actual coverage depends on product, color change, texture, porosity and application. The surface and waste allowances are editable assumptions, not manufacturer guarantees. Measure actual wall shapes for vaulted, sloped or irregular rooms. Allow separately for primer, trim and additional surfaces.

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