Quick Formula
Gallons = (Wall Area × Coats) ÷ Coverage Rate
Standard coverage: 350 sq ft per gallon
Example: 400 sq ft × 2 coats ÷ 350 = 2.3 gallons
Use our Paint Coverage Calculator to get exact gallons for your room.
Step 1: Calculate Wall Area
For Rectangular Rooms
Formula: 2 × (Length + Width) × Height
Example: Room is 12 ft × 10 ft with 8 ft ceilings
Wall Area = 2 × (12 + 10) × 8 = 352 sq ft
Subtract Doors and Windows
For more accurate estimates, subtract door and window areas:
- Standard door: 20 sq ft (3 ft × 6.5 ft)
- Standard window: 15 sq ft (3 ft × 5 ft)
- Large window: 30 sq ft (5 ft × 6 ft)
Example: 352 sq ft wall area
Subtract 2 doors (40 sq ft) and 2 windows (30 sq ft)
Paintable Area = 352 - 70 = 282 sq ft
Step 2: Understand Coverage Rates
Standard Coverage Rates
| Paint Type | Coverage per Gallon | Notes |
|---|---|---|
| Premium Paint | 350-400 sq ft | Best coverage |
| Standard Paint | 300-350 sq ft | Average quality |
| Budget Paint | 250-300 sq ft | May need extra coats |
| Primer | 200-300 sq ft | Lower coverage |
| Ceiling Paint | 350-400 sq ft | Flat finish |
Factors Affecting Coverage
- •
Surface Texture
Rough or porous surfaces absorb more paint. Textured walls may need 20-30% more paint.
- •
Color Change
Dark to light or light to dark requires extra coats. Use tinted primer to reduce coats needed.
- •
Application Method
Rollers provide best coverage. Sprayers use 20-30% more paint but save time on large projects.
- •
Paint Quality
Premium paints have better coverage and hide imperfections with fewer coats.
Step 3: Determine Number of Coats
1 Coat Situations
- • Touch-ups and minor repairs
- • Same color refresh
- • Premium paint over primer
2 Coats (Most Common)
- • Standard repainting projects
- • Similar color changes
- • New drywall with primer
- • Professional finish quality
3+ Coats
- • Dramatic color changes (dark to light)
- • Covering bold colors or patterns
- • Budget paint with poor coverage
- • Highly textured surfaces
Step 4: Calculate Paint Needed
Example 1: Standard Bedroom
Room: 12 ft × 10 ft, 8 ft ceilings
Wall Area: 2 × (12 + 10) × 8 = 352 sq ft
Subtract: 1 door (20 sq ft) + 1 window (15 sq ft) = 35 sq ft
Paintable Area: 352 - 35 = 317 sq ft
Coats: 2
Total Area: 317 × 2 = 634 sq ft
Coverage Rate: 350 sq ft/gallon
Paint Needed: 634 ÷ 350 = 1.8 gallons (buy 2 gallons)
Example 2: Living Room with Ceiling
Room: 20 ft × 15 ft, 9 ft ceilings
Wall Area: 2 × (20 + 15) × 9 = 630 sq ft
Ceiling Area: 20 × 15 = 300 sq ft
Subtract: 2 doors (40 sq ft) + 3 windows (45 sq ft) = 85 sq ft
Paintable Walls: 630 - 85 = 545 sq ft × 2 coats = 1,090 sq ft
Ceiling: 300 sq ft × 2 coats = 600 sq ft
Wall Paint: 1,090 ÷ 350 = 3.1 gallons (buy 4 gallons)
Ceiling Paint: 600 ÷ 350 = 1.7 gallons (buy 2 gallons)
Example 3: Accent Wall
Wall: 12 ft wide × 8 ft tall = 96 sq ft
Coats: 2 (bold color)
Total Area: 96 × 2 = 192 sq ft
Paint Needed: 192 ÷ 350 = 0.55 gallons (buy 1 quart or 1 gallon)
Primer Guide
When to Use Primer
- ✓
New drywall: Always prime bare drywall before painting
- ✓
Dramatic color changes: Use tinted primer to reduce topcoats needed
- ✓
Stain blocking: Cover water stains, smoke damage, or wood tannins
- ✓
Glossy surfaces: Prime glossy paint or varnish for better adhesion
Primer Coverage
Primer typically covers 200-300 sq ft per gallon. Calculate primer separately from paint using the same wall area formula.
Paint Finish Guide
| Finish | Sheen | Best For |
|---|---|---|
| Flat/Matte | No shine | Ceilings, low-traffic areas |
| Eggshell | Slight sheen | Living rooms, bedrooms |
| Satin | Soft shine | Kitchens, bathrooms, hallways |
| Semi-Gloss | Noticeable shine | Trim, doors, cabinets |
| Gloss | High shine | Furniture, accent pieces |
Money-Saving Tips
- $
Buy 5-gallon buckets
Save $5-10 per gallon by buying in bulk for large projects.
- $
Use our calculator
Our paint calculator prevents over-purchasing expensive premium paints.
- $
Shop holiday sales
Memorial Day, Labor Day, and Black Friday offer 20-40% discounts.
- $
Invest in quality
Premium paint covers better, reducing coats needed and saving time.
- $
Keep leftovers
Store paint properly for touch-ups instead of buying new cans.
Frequently Asked Questions
How much does one gallon of paint cover?
One gallon covers 350-400 sq ft per coat with premium paint. Budget paints may only cover 250-300 sq ft per gallon.
Do I need to paint the ceiling?
Ceilings should be painted every 5-10 years or when walls are painted. Calculate ceiling paint separately using length × width.
How long does paint last?
Unopened paint lasts 2-10 years. Opened paint lasts 2-5 years if sealed properly. Store in a cool, dry place away from freezing temperatures.
Can I return unused paint?
Most stores accept returns of unopened, unmixed paint within 30-90 days. Custom-mixed colors typically cannot be returned.
Calculate Your Paint Needs
Use our free paint calculator to get instant, accurate estimates for your project.