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Paint Calculator

Separate wall and ceiling paint from coverage and coats.

Your project

Enter your measurements. Required fields are labeled; assumptions and optional quotes can be edited below.

Loading measurement inputs…

Calculator inputs
Room length Required
Enter whole feet and inches less than 12. One blank component means 0.
Room width Required
Enter whole feet and inches less than 12. One blank component means 0.
Room height Required
Enter whole feet and inches less than 12. One blank component means 0.
Door and window openings

Optional wall deductions. Enter actual sizes and counts; no standard opening sizes are assumed.

Up to 20 opening rows; each count applies to the entered size.

Paint products

Applied preset: US-market. No assumptions changed. Display units do not select a market preset.

Wall paint product
1–10 coats. Coverage below is per single coat.
Per coat; use the paint label. Supported range: 4.07–2037.29 ft²/US gal/coat.
0–50%. Additional liquid before can rounding; no hidden losses.
Physical size of one can, 0.03–7.93 US gal. Unit toggles preserve can identity.
Wall optional cost
Optional supplied can price. Zero is valid; unpriced products are not free.

How this calculator works

Enter a rectangular room’s length, width and height to measure four walls, or enter gross measured wall area before openings. Optional door/window rows use width × height × count. Openings must total less than gross wall area. Ceiling paint is optional and always a separate product; in known-wall-area mode its measured area is required.

Paint estimate formulaeach product liquid = net area × coats ÷ coverage per coat × (1 + allowance); cans = ceil(required liquid ÷ selected can size)

Assumptions and limitations

Wall and ceiling paint round independently; their cans are never pooled. Coverage is a planning assumption from the product label, not a coverage guarantee. Openings reduce only walls. Primer, trim, labor, surface preparation quantities and mixed-can optimization are excluded. Square Footage does not prefill Paint because transferred area could already be net of openings.

Allowance is the additional requirement before purchase rounding. Purchase surplus is the capacity bought beyond that adjusted requirement. These are separate quantities. Prices are optional user-entered USD quotes, including valid zero prices; they exclude tax, delivery and labor. Missing prices never imply a free product.

US/Metric changes representation only. An explicit market preset changes its listed product assumptions; it does not change project geometry. Required project measurements begin blank, and every active row must be valid before a result is shown.

Worked examples

PAINT-01: A 12 × 10 × 8 ft room has 352 ft² of walls. One 3 × 7 ft door and two 3 × 4 ft windows deduct 45 ft², leaving 307 ft². Two coats at 350 ft²/US gal/coat need 614/350 US gal and 2 one-gallon wall cans. The 120 ft² ceiling needs 240/350 US gal and 1 separate can. At $40/wall can and $30/ceiling can, cost is $110.00.

PAINT-02: Gross walls of 50 m² less one 2 × 1 m opening leave 48 m². Two coats at 10 m²/L/coat need 9.6 L base. With 5% allowance, 10.08 L requires 5 cans of 2.5 L, buying 12.5 L. At $25/can, cost is $125.00.

Check the label’s coverage, coat count, can size and surface preparation instructions. Partial pricing excludes unpriced active products.

Methodology and conversion rules

Guides

Person measuring the width of an empty room with a tape measure stretched across the floor

How to Measure Square Footage of a Room

Learn how to measure room square footage accurately, including rectangular and irregular rooms, alcoves, closets and common measurement mistakes.

Paint roller, tray and open paint can beside a wall prepared for painting

Paint Coverage per Gallon: What the Numbers Really Mean

Understand paint coverage per gallon, how coats and wall condition change the estimate, and how to turn measured area into practical container quantities.