Paint Calculator
Calculate how much paint a surface needs from its area, coats and paint coverage.
Formula and sources updated · Data sources · 1View algorithm, constants and default inputs (JSON)
About this calculator
Enter the coverage stated on the paint label; actual coverage varies by product and surface. Gallons are rounded up to whole 1-gallon cans for the estimate, and cost uses that rounded count. Primer and other pack sizes are not included.
Worked example
calculated with the default values below
Surface area 800 sq ft · Number of coats 2 · Coverage per gallon 350 sq ft · Price per gallon 35 $ Cans to buy 5 · Gallons needed 4.57 gal · Total area to paint 1,600 sq ft · Estimated cost 175.00 $
Method and assumptions
G = A × C ÷ R; cans = ceil(G); cost = cans × P Cans are always rounded up to whole units; R = 0 falls back to the default coverage of 350. Enter the coverage stated on the paint label; actual coverage varies by product and surface. Gallons are rounded up to whole 1-gallon cans for the estimate, and cost uses that rounded count. Primer and other pack sizes are not included. Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
Data sources
Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
G = A × C ÷ R; cans = ceil(G); cost = cans × P
- A
- Paintable area (sq ft)
- C
- Number of coats
- R
- Coverage (sq ft per gallon, default 350)
- P
- Price per gallon
Cans are always rounded up to whole units; R = 0 falls back to the default coverage of 350.
Frequently asked questions
Why does adding a second coat nearly double the gallons I need?
Total area is surface times coats, so 800 sq ft with 2 coats is 1,600 sq ft to cover. At the default 350 sq ft per gallon that is 4.57 gallons, rounded up to 5 cans at $35 each, about $175. Lower the coverage to a realistic 300 for textured walls and you need 6 cans; raising it to 400 drops you to 4. The coverage field drives the answer far more than price.
Which inputs and limits apply to Paint Calculator?
Use the units shown beside each field. These are form limits, not recommended settings. Surface area: 0–100,000 sq ft; Number of coats: 1–5; Coverage per gallon: 50–800 sq ft; Price per gallon: 0–300 $ G = A × C ÷ R; cans = ceil(G); cost = cans × P Cans are always rounded up to whole units; R = 0 falls back to the default coverage of 350. Enter the coverage stated on the paint label; actual coverage varies by product and surface. Gallons are rounded up to whole 1-gallon cans for the estimate, and cost uses that rounded count. Primer and other pack sizes are not included. Use the cited guidance and your own measurements, bills or product specifications to choose inputs. Sample defaults are not current local data.
What is a complete worked example for Surface area = 800 sq ft; Number of coats = 2?
Inputs: Surface area = 800 sq ft; Number of coats = 2; Coverage per gallon = 350 sq ft; Price per gallon = 35 $. Calculation: G = A × C ÷ R; cans = ceil(G); cost = cans × P. Results: Cans to buy = 5; Gallons needed = 4.57 gal; Total area to paint = 1,600 sq ft; Estimated cost = 175.00 $.