How much extra paint should I buy?
Add about 10% for touch-ups, roller tray waste, and future patch jobs. The calculator includes a waste allowance you can adjust.
Interior Paint Calculator
Interior latex for walls and ceilings — with default 350 sq ft per gallon and two coats. Toggle walls only, ceiling only, or both for a whole-room repaint.
Rooms
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Project settings
Default 10% for touch-ups
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Choosing the right sheen indoors
Flat and matte hide imperfections on ceilings and low-traffic bedrooms. Eggshell and satin wash better in kitchens, halls, and kids’ rooms. Our interior paint sheen guide matches finish to each room.
Higher sheen covers slightly less area per gallon — if you switch from flat to semi-gloss, nudge coverage down 10–15% in settings.
Waste allowance — what it covers
The default 10% waste covers roller tray residue, touch-up jars, and cutting-in overlap. Bold colour changes or porous new drywall may need 15%.
Trim and doors are not included in wall/ceiling area — most homeowners buy a separate quart of trim paint. Factor that in when budgeting.
Related guides
Frequently asked questions
Can I calculate multiple rooms?
Yes. Add up to five rooms and the calculator totals paintable area, deductions, and gallons for the whole job.
Does this work for trim and doors?
This tool focuses on wall and ceiling area. Trim and doors use less paint — many DIYers buy a quart of trim paint separately.
Related calculators
Paint Calculator · https://paint-calculator.ca/interior-paint-calculator/