Paint Calculator - Calculate Paint & Primer

Paint Calculator - Calculate Paint Needs

Calculate paint requirements instantly with our free calculator. Get accurate estimates for interior and exterior painting projects including gallons needed, primer requirements, and total project cost.

Calculate Your Paint Needs

Project Type:

• Interior Walls
• Exterior Walls
• Ceiling
• Trim/Doors
• All Surfaces

[Select Project Type]

Room Dimensions:

• Room Length: [Input] feet
• Room Width: [Input] feet
• Wall Height: [Input] feet (standard 8')

Surface Details:

• Number of Coats: [Dropdown: 1, 2, 3]
• Surface Condition: [Dropdown: New/Painted, Raw Drywall, Dark to Light, Patched]
• Include Ceiling: [Checkbox]
• Include Trim: [Checkbox]

[Calculate Button]

Your Results:

• Wall Surface Area: [Amount] sq ft
• Paint Needed (including coats): [Amount] gallons
• Primer Needed: [Amount] gallons (if applicable)
• Total Project Cost: $[Amount]

---

What is Paint Coverage?

Paint Coverage refers to the area that one gallon of paint will cover. Most paint manufacturers state coverage on the can, typically 350-400 square feet per gallon.

Standard Coverage Rates

Paint Type	Coverage per Gallon
Interior Paint	350-400 sq ft
Exterior Paint	250-350 sq ft
Primer	200-300 sq ft
Ceiling Paint	350-400 sq ft
High-Hide/One-Coat	400-450 sq ft
Textured/Rough	150-250 sq ft

Factors Affecting Coverage

Reduces Coverage:

• Rough or textured surfaces
• Unprimed surfaces
• Color changes (especially dark to light)
• Porous surfaces (new drywall, bare wood)
• Spray application (more overspray)

Improves Coverage:

• Smooth, prepainted surfaces
• Same-color repaints
• Proper primer application
• Quality paint and tools

How to Calculate Paint Needs

Calculating Wall Area

Formula:

(Perimeter × Height) - Openings = Wall Surface Area

Example (12' × 14' room, 8' ceilings):

Perimeter: (12 + 14) × 2 = 52 linear feet
Total Wall Area: 52 × 8 = 416 sq ft

Subtract Openings:
- Window: 3' × 4' = 12 sq ft
- Door: 3' × 6'8" (6.67') = 20 sq ft
Total Openings: 32 sq ft

Net Wall Area: 416 - 32 = 384 sq ft

Calculating Ceiling Area

Formula:

Length × Width = Ceiling Area

Example:

Ceiling: 12' × 14' = 168 sq ft

Calculating Paint Needed

Formula:

(Surface Area ÷ Coverage Rate) × Number of Coats = Gallons Needed

Example (384 sq ft walls, 350 coverage, 2 coats):

First coat: 384 ÷ 350 = 1.1 gallons
Second coat: 384 ÷ 350 = 1.1 gallons
Total: 2.2 gallons
Round up: 3 gallons

Multiple Rooms

Total all rooms:

Room 1 + Room 2 + Room 3... = Total Surface Area
Then calculate paint needed

Example:

Living Room: 384 sq ft
Bedroom 1: 320 sq ft
Bedroom 2: 320 sq ft
Hallway: 180 sq ft
Total: 1,204 sq ft

Paint (2 coats): (1,204 ÷ 350) × 2 = 6.9 gallons
Buy: 7 gallons

Interior Paint Calculator

Walls Only

Standard Room Example:

Room: 12' × 14' with 8' ceilings
Wall area: 384 sq ft (after openings)

Two coats of paint:
(384 ÷ 350) × 2 = 2.2 gallons
Buy: 3 gallons

Walls and Ceiling

Example:

Walls: 384 sq ft
Ceiling: 168 sq ft
Total: 552 sq ft

Two coats walls:
(384 ÷ 350) × 2 = 2.2 gallons

One coat ceiling:
168 ÷ 350 = 0.48 gallons
Buy: 1 gallon

Including Trim and Doors

Trim Areas:

• Baseboard: Perimeter × Height
• Door casing: Perimeter of doors × Width
• Window casing: Perimeter of windows × Width

Example:

Baseboard: 52' × 4" (0.33') = 17 sq ft
Door casing: 20' × 3" (0.25') = 5 sq ft
Window casing: 14' × 3" (0.25') = 3.5 sq ft
Total trim: 25.5 sq ft

Paint (2 coats):
(25.5 ÷ 350) × 2 = 0.15 gallons
Included with wall paint (buy 3 gallons total)

Exterior Paint Calculator

Calculating Exterior Surface Area

Formula:

(Perimeter × Height) - Openings = Exterior Wall Area

Example (30' × 40' house, 10' walls):

Perimeter: (30 + 40) × 2 = 140 linear feet
Wall Area: 140 × 10 = 1,400 sq ft

Subtract Openings:
- Windows: 8 windows × 15 sq ft = 120 sq ft
- Doors: 2 doors × 20 sq ft = 40 sq ft
Total Openings: 160 sq ft

Net Wall Area: 1,400 - 160 = 1,240 sq ft

Exterior Paint Needed

Lower coverage (300 sq ft per gallon):

Example:

Wall area: 1,240 sq ft
Coverage: 300 sq ft/gallon (exterior)
Coats: 2

Paint needed: (1,240 ÷ 300) × 2 = 8.3 gallons
Buy: 9 gallons

Including Soffits and Trim

Soffits:

Perimeter × Overhang depth = Soffit Area

Example:

Perimeter: 140' × 2' overhang = 280 sq ft
Paint (2 coats): (280 ÷ 300) × 2 = 1.9 gallons

Trim:

• Fascia, corner boards, window trim
• Add 10-15% to wall area for trim

Primer Calculator

When to Use Primer

Use Primer:

• New drywall or bare wood
• Patched areas (large patches)
• Color changes (especially dark to light)
• Glossy surfaces being repainted
• Stained or water-damaged areas
• Raw plaster or masonry

May Not Need Primer:

• Same-color repaints
• Paint already in good condition
• Using paint-and-primer-in-one products

Calculating Primer Needed

Formula:

Surface Area ÷ Primer Coverage Rate = Gallons of Primer

Primer Coverage:

• New drywall: 200-250 sq ft/gallon
• Bare wood: 250-300 sq ft/gallon
• Previously painted: 300-350 sq ft/gallon

Example (New Drywall):

Wall area: 384 sq ft
Coverage: 250 sq ft/gallon
Primer needed: 384 ÷ 250 = 1.5 gallons
Buy: 2 gallons

Spot Priming

For Patches:

• Estimate patch area
• Usually 1 quart is sufficient for most rooms

Rule:

If patch area is less than 20% of total, spot prime only

Paint Finish Types

Sheen Levels

Finish	Characteristics	Best For
Flat/Matte	No shine, hides imperfections	Ceilings, low-traffic areas
Eggshell	Low sheen, washable	Living rooms, bedrooms, halls
Satin	Soft sheen, very washable	Kitchens, baths, trim
Semi-Gloss	Shiny, durable	Trim, doors, cabinets
High-Gloss	Very shiny, most durable	Furniture, doors, accents

Selecting the Right Finish

Walls:

• High traffic: Satin or eggshell
• Low traffic: Flat or eggshell
• Kids' rooms: Eggshell or satin

Trim:

• Semi-gloss for easy cleaning
• High-gloss for dramatic look

Ceilings:

• Flat exclusively
• Ceiling paint specifically formulated

Number of Coats

Standard Guidelines

Two Coats:

• Most interior/exterior projects
• Color changes
• New construction
• Quality results

One Coat:

• Same-color repaints
• Using high-hide "one-coat" paint
• Touch-ups and small areas

Three Coats:

• Drastic color changes
• Painting over dark colors
• Uneven substrate
• Extra durability needed

Coat Coverage

Realistic Coverage:

Coat	Coverage %
First Coat	70-80% of rated coverage
Second Coat	90-100% of rated coverage
Third Coat	100%+ (builds thickness)

Example:

Wall area: 350 sq ft
First coat: 350 ÷ 280 (80%) = 1.25 gallons
Second coat: 350 ÷ 315 (90%) = 1.1 gallons
Total: 2.35 gallons (buy 3)

Cost Estimation

Paint Prices (2024 averages)

Interior Paint:

• Economy/Contractor: $15-$25 per gallon
• Mid-Grade: $30-$45 per gallon
• Premium: $50-$70+ per gallon

Exterior Paint:

• Economy: $25-$35 per gallon
• Mid-Grade: $40-$60 per gallon
• Premium: $70-$100+ per gallon

Primer:

• Standard: $15-$25 per gallon
• Multi-purpose: $25-$35 per gallon
• Specialty (stain-blocking): $35-$50 per gallon

Complete Project Cost Example

Interior Room (12' × 14', 8' ceilings):

Paint Needed:

• Walls: 3 gallons (2 coats)
• Ceiling: 1 gallon
• Total Paint: 4 gallons

Material Cost:

• Wall paint (mid-grade): 3 × $35 = $105
• Ceiling paint: 1 × $30 = $30
• Primer (if needed): 2 × $20 = $40
• Paint Total: $105 + $30 + $40 = $175

Supplies:

• Brushes and rollers: $40
• Tape and drop cloths: $30
• Tray and liners: $15
• Supplies Total: $85

Materials Total: $175 + $85 = $260

Labor (DIY): $0 Labor (Hired): $200-$400

Project Total:

• DIY: $260
• Hired: $460-$660

Exterior House Example

1,240 sq ft exterior walls:

Paint:

• Body: 9 gallons × $50 = $450
• Trim: 2 gallons × $55 = $110
• Paint Total: $560

Supplies:

• Brushes, rollers, spray equipment: $150
• Tape, drop cloths, caulk: $80
• Supplies Total: $230

Materials Total: $560 + $230 = $790

Labor (Hired): $2,000-$4,000

Project Total:

• DIY: $790
• Hired: $2,790-$4,790

Paint Quality

Quality Levels

Economy/Contractor Grade:

• Lower pigment concentration
• Less durable
• May require more coats
• Best for: Rental properties, temporary situations

Mid-Grade:

• Good pigment and durability
• Most homeowners' choice
• Good coverage
• Best for: Most residential projects

Premium:

• Highest pigment concentration
• Best coverage and durability
• Washable, stain-resistant
• Best for: High-traffic areas, luxury homes

Paint Calculator Adjustments

Economy Paint:

• Subtract 10% from coverage rate
• Add extra coat for difficult colors

Premium Paint:

• Use full coverage rate
• May achieve one-coat coverage on same colors

Common Mistakes

Mistake 1: Not Accounting for Multiple Coats

Problem: Calculating based on single coat coverage

Solution: Always calculate for 2 coats minimum. Subtract 10-20% from coverage for first coat

Mistake 2: Ignoring Surface Texture

Problem: Using standard coverage for textured walls

Solution: Textured surfaces reduce coverage 20-40%. Use 200-250 sq ft per gallon for heavy texture

Mistake 3: Forgetting Primer

Problem: Not accounting for primer in calculations

Solution: Add primer cost and calculate separately (lower coverage than paint)

Mistake 4: Underestimating Color Change

Problem: Using standard coverage for dramatic color changes

Solution: Dark to light may need 3 coats or tinted primer. Adjust calculations accordingly

Mistake 5: Not Buying Extra

Problem: Buying exact calculated amount

Solution: Always buy 10% extra for touch-ups. Keep leftover paint for future repairs

How do I calculate how much paint I need?

Measure the room's perimeter and height to get wall area. Subtract windows and doors. Divide by paint coverage rate (350 sq ft/gallon typical). Multiply by number of coats. Always round up.

How many gallons of paint do I need for a 12 × 12 room?

12' × 12' room with 8' ceilings: Walls = (12+12) × 2 × 8 = 384 sq ft. Subtract ~30 sq ft for openings = 354 sq ft. Two coats: (354 ÷ 350) × 2 = 2 gallons. Buy 2-3 gallons.

How much does 1 gallon of paint cover?

Standard coverage: 350-400 square feet per gallon. Primer covers 200-300 sq ft. Rough or textured surfaces: 150-250 sq ft. Coverage varies by paint quality and surface condition.

Should I use primer or paint with primer?

Use separate primer for: new drywall, bare wood, major color changes, stained surfaces. Paint-and-primer-in-one works for: same-color repaints, minor color changes, already-painted surfaces in good condition.

How many coats of paint do I need?

Two coats is standard for most projects. One coat for same-color repaints. Three coats for: dramatic color changes (especially dark to light), painting over dark colors, uneven surfaces.

How much extra paint should I buy?

Buy 10% extra for touch-ups and mistakes. Always keep leftover paint for future touch-ups. Unopened paint lasts for years; opened paint lasts 2-5 years if sealed properly.

Do I need to paint ceiling before walls?

Paint ceiling first for best results. Prevents drips on walls. Easier to cut in walls to ceiling than vice versa. Use different paint (ceiling flat vs wall eggshell).

How much does it cost to paint a room interior?

DIY: Paint ($80-$150) + supplies ($80-$100) = $160-$250 per average room. Hired: $2-$4 per sq ft = $300-$600 per average room, including materials.

---

Practice Examples

Example 1: Bedroom Paint Calculation

Room:

• 10' × 12' with 8' ceilings
• 2 windows (3' × 4')
• 1 door (3' × 6'8")

Calculation:

Perimeter: (10 + 12) × 2 = 44'
Wall area: 44 × 8 = 352 sq ft
Openings: (3 × 4 × 2) + (3 × 6.67) = 24 + 20 = 44 sq ft
Net walls: 352 - 44 = 308 sq ft

Paint (2 coats): (308 ÷ 350) × 2 = 1.76 gallons
Buy: 2 gallons

Example 2: Exterior House

House:

• 28' × 40' footprint
• 10' wall height
• 10 windows (15 sq ft each)
• 2 doors (20 sq ft each)

Calculation:

Perimeter: (28 + 40) × 2 = 136'
Wall area: 136 × 10 = 1,360 sq ft
Openings: (10 × 15) + (2 × 20) = 190 sq ft
Net walls: 1,360 - 190 = 1,170 sq ft

Paint (2 coats, 300 coverage): (1,170 ÷ 300) × 2 = 7.8 gallons
Buy: 8 gallons

---

Related Calculators

• Wallpaper Calculator
• Room Size Calculator
• Flooring Calculator
• Drywall Calculator
• Tile Calculator

---

Need Help? Our paint calculator is perfect for homeowners, contractors, and DIYers. Calculate your paint needs now!