Paint Calculator
Calculate how much paint you need for interior or exterior painting projects. Automatically deducts doors and windows, includes primer calculations, and provides cost estimates. Get results in gallons and liters with coverage rates customized to your paint quality.
How It Works
1. Enter Room Dimensions
Input the length, width, and height of your room in feet or meters. For multiple rooms, calculate each room separately and add the results.
2. Specify Openings
Enter the number of doors and windows. The calculator automatically deducts standard sizes (doors: 21 sq ft, windows: 15 sq ft) from the total area.
3. Set Paint Details
Choose number of coats (typically 2), coverage rate (usually 350-400 sq ft per gallon), and whether to include primer and ceiling.
4. Get Results & Cost
See gallons needed for paint and primer, total area to cover, and optional cost estimate. Results include both imperial and metric measurements.
Examples
Example 1: Bedroom (Walls Only)
Room: 12' × 10' × 8' high Walls: 4 Doors: 1 Windows: 2 Coats: 2 Primer: Yes Paint Ceiling: No Coverage: 350 sq ft/gallon Results: Total Area: 331 sq ft (30.7 m²) Paint Needed: 2 gallons Primer Needed: 1 gallon A standard bedroom with 4 walls. After deducting 1 door (21 sq ft) and 2 windows (30 sq ft), need 2 gallons of paint for 2 coats plus 1 gallon primer.
Example 2: Living Room with Ceiling
Room: 16' × 14' × 9' high Walls: 4 Doors: 2 Windows: 3 Coats: 2 Primer: Yes Paint Ceiling: Yes Coverage: 350 sq ft/gallon Paint: $35/gallon Primer: $25/gallon Results: Total Area: 719 sq ft (66.8 m²) Paint Needed: 5 gallons Primer Needed: 3 gallons Estimated Cost: $250 Larger living room including ceiling (16×14=224 sq ft). With doors/windows deducted: walls 498 sq ft + ceiling 224 sq ft = 722 sq ft total.
Example 3: Bathroom (Small)
Room: 6' × 5' × 8' high Walls: 4 Doors: 1 Windows: 1 Coats: 2 Primer: Yes Paint Ceiling: Yes Coverage: 350 sq ft/gallon Results: Total Area: 140 sq ft (13.0 m²) Paint Needed: 1 gallon Primer Needed: 1 gallon Small bathroom including ceiling. One gallon of paint covers 350 sq ft, enough for 2 coats on 140 sq ft (with some left over).
Frequently Asked Questions
How much area does one gallon of paint cover?
One gallon of paint typically covers 350-400 square feet per coat on smooth surfaces like drywall. Coverage is reduced to 250-300 square feet per gallon on rough, textured, or porous surfaces like concrete, brick, or textured walls. Quality paints often have better coverage. Always check the paint can label for the manufacturer's coverage rate.
Do I need to use primer?
Use primer when painting new drywall, covering dark colors with light paint, painting over stains or repairs, switching from oil to latex paint, or painting glossy surfaces. Primer seals the surface, improves paint adhesion, and provides better coverage. You can skip primer if repainting the same color over clean, well-prepared walls.
How many coats of paint do I need?
Most painting projects require 2 coats for proper coverage and color depth. Use 1 coat if repainting the same color over clean walls with quality paint. Use 3 coats for dramatic color changes (dark to light or vice versa), or when using lower-quality paint. Always apply primer first when needed, then count paint coats separately.
Should I paint the ceiling the same as walls?
Ceilings are typically painted white or off-white to reflect light and make rooms feel larger. Painting ceilings the same color as walls can create a cozy, enveloping effect in bedrooms or studies. Dark ceiling paint can make a room feel smaller but more intimate. Consider room size, natural light, and desired atmosphere when deciding.
How do I reduce paint waste and save money?
Measure accurately to avoid buying excess paint. Buy quality paint that covers better (may need only 1-2 coats instead of 3). Use primer on new surfaces for better coverage. Store leftover paint properly for touch-ups (sealed can in cool, dry place). Buy paint on sale or in larger quantities for multiple rooms. Consider paint + primer combination products for some projects.