Construction Calculators
Paint Calculator
Estimate paint gallons for rooms, walls, ceilings, doors, windows, coats, primer, and cost.
Paint project details
Estimate paint gallons for rooms, walls, ceilings, doors, windows, coats, primer, and cost.
Subtract openings
Door and window dimensions use the same unit as the main project dimensions.
Coverage presets
Coverage varies by paint product, surface texture, color change, and application method. Check the paint label for exact coverage.
Extra presets
Enter room or wall dimensions to estimate paint in gallons. Add doors, windows, coats, primer, coverage, and price for a more useful estimate.
The result will show area, openings, coats, paint gallons, primer, liters, and optional cost.
Paint calculator formula
Room wall area = 2 x (length + width) x height.
Wall area = length x height.
Ceiling area = length x width.
Net area = gross area - doors/windows.
Paintable area = net area x coats, plus selected extra percentage.
Paint gallons = paintable area / coverage per gallon. Paint to buy is rounded up.
Primer gallons = net area x primer coats / primer coverage, plus selected extra percentage.
Cost = rounded paint and primer gallons x price per gallon.
Worked examples
A 12 ft x 10 ft room with 8 ft walls has 352 sq ft of gross wall area. Subtract one 3 ft x 7 ft door and two 3 ft x 4 ft windows for 307 sq ft net area. With 2 coats, paintable area is 614 sq ft. At 350 sq ft per gallon, that is 1.754 gallons, so buy 2 gallons.
A 12 ft x 10 ft ceiling is 120 sq ft. With 2 coats, paintable area is 240 sq ft. At 350 sq ft per gallon, that is 0.686 gallons, so buy 1 gallon.
For primer, 307 sq ft with 1 primer coat at 300 sq ft per gallon needs about 1.023 gallons, so buy 2 gallons if using full-gallon containers.
Common mistakes
- Forgetting to subtract doors and windows when precision matters.
- Forgetting the number of coats.
- Using one universal coverage number for every paint.
- Not adding extra for rough surfaces, touchups, or roller loss.
- Confusing square feet with linear feet.
- Rounding down paint gallons.
- Ignoring primer for new drywall or major color changes.
Measure before you buy
If you still need wall or ceiling area, use the Square Footage Calculator or Area Calculator. Default coverage is only an estimate, so always check your paint label for the manufacturer's coverage rate.
Quick answers
What this calculator answers
- Result: Estimate paint gallons, primer gallons, liters, and cost for rooms, walls, ceilings, or manual area.
- Formula: Paint gallons = net area x coats / coverage per gallon, with optional extra added.
- Best use: Use it before buying paint, then check the paint label for exact product coverage. square footage calculator
Transparency note
Accuracy and limitations
Calzivo tools are built for practical estimates, conversions, and checks. Some tools use standard formulas or simplified assumptions, and results can be affected by input accuracy, rounding, units, local rules, or changing official requirements.
Construction estimates can vary with site conditions, waste, compaction, product coverage, local requirements, and measurement accuracy. Verify material orders before purchasing.
How to Use This Tool
Use these steps to enter the right inputs and interpret the result correctly.
Choose room walls, single wall, ceiling, or manual area mode.
Enter dimensions, coats, and paint coverage.
Subtract doors and windows for wall estimates if needed.
Add primer, extra percentage, and price for a fuller project estimate.
Related Tools
Other helpful tools in the Construction Calculators category.
Square Footage Calculator
Calculate square footage for rooms, walls, flooring, paint, concrete, gravel, and other material planning.
Area Calculator
Calculate the area of any geometric shape.
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Calculate cubic yards from length, width, and depth for gravel, sand, concrete, mulch, topsoil, fill, and other bulk materials.
Square Feet to Cubic Yards Calculator
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Concrete Calculator
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Related Guides
Background reading and explanations related to Paint Calculator.
Frequently Asked Questions
Common questions about Paint Calculator and how to read the result.
How do I calculate how much paint I need?
Calculate the paintable area, multiply by the number of coats, then divide by the paint coverage per gallon.
How much area does one gallon of paint cover?
A common planning estimate is about 350 square feet per gallon, but actual coverage depends on the paint product and surface.
Should I subtract doors and windows?
Yes, subtract large openings when you want a tighter wall estimate. Small openings may not change the purchase amount after rounding.
How many coats of paint should I calculate?
Two coats is common for many repainting projects, but new drywall, dark color changes, and rough surfaces may need primer or extra coats.
How do I calculate paint for a ceiling?
Multiply ceiling length by width, then multiply by coats and divide by coverage per gallon.
Do I need primer?
Primer can help for new drywall, stains, porous surfaces, or major color changes. Check product guidance for your project.
Should I round up paint gallons?
Usually yes. Paint is sold in fixed container sizes, and rounding down can leave you short for coverage or touchups.