Interior Paint Coverage Estimator

Estimate exactly how many buckets of paint to buy — no more guessing, no mid-project runs to the hardware store.

What it computes. Wall area = room perimeter × wall height, minus a standard deduction per door (1.9 m²) and window (1.5 m²). Multiply by the number of coats, add the waste factor (typically 10%), then divide by your paint's coverage (m² per liter) and bucket size to get the number of buckets, rounded up.

Options explained.

• Coverage (m²/L) — printed on the can; wall paint is usually 10–14 m²/L per coat. Premium/lower-quality paints differ widely.
• Coats — usually 2 for a color change, 1 for a refresh of the same shade.
• Waste factor — leftover in the tray, roller absorption, touch-ups. 10% is standard.
• Ceiling — adds floor area (length × width) to the paintable surface.
• Primer — recommended for bare drywall, drastic color changes, or repaired patches; one coat at roughly the same coverage.

Why bucket rounding matters. Paint is sold by the bucket, not by the liter. If you need 4.1 buckets, you buy 5 — the estimator always rounds up.

Practical tips.

• Measure at the longest wall; closets and alcoves add hidden area.
• Two coats of a deep red or yellow over white may need a tinted primer.
• Keep ~250 mL for future touch-ups: store in a small airtight jar, label with room name and date.