Quick Reference
- •Wall area: Length × Height for each wall
- •Floor area: Length × Width
- •Standard ceiling: 8 feet (96 inches)
- •Always measure in inches for precision, then convert
Tools You'll Need
Required
- • 25-foot tape measure (minimum)
- • Pencil and paper or phone calculator
- • Ladder (for high measurements)
Helpful
- • Laser measure (for accuracy)
- • Level (to check for plumb walls)
- • Camera (to document room layout)
Step-by-Step Measurement Process
1Measure Wall Length
Measure along the baseboard from corner to corner. Hold tape measure level.
Tips:
- • Don't measure diagonally
- • Measure at any height - wall length is the same top to bottom
- • Measure each wall separately - rooms are rarely perfect rectangles
2Measure Wall Height
Measure from floor to ceiling. Standard residential height is 96 inches (8 feet).
Common Heights:
- • Standard: 96 inches (8 feet)
- • Newer homes: 108 inches (9 feet)
- • Vaulted: Varies - measure at multiple points
3Calculate Wall Area
Multiply length by height for each wall. Convert inches to feet first (divide by 12).
Formula:
Wall Area (sq ft) = (Length in inches ÷ 12) × (Height in inches ÷ 12)Example: Wall is 144" long × 96" high
(144 ÷ 12) × (96 ÷ 12) = 12 ft × 8 ft = 96 sq ft4Subtract Openings
Measure doors and windows to subtract from total wall area.
Standard Sizes:
Doors
- • Standard interior: 80" × 30" = 16.7 sq ft
- • Standard exterior: 80" × 36" = 20 sq ft
Windows
- • Small: 24" × 36" = 6 sq ft
- • Standard: 36" × 48" = 12 sq ft
- • Large: 48" × 60" = 20 sq ft
Calculating Floor Area
Floor area is simpler - just length times width. For irregular rooms, break into rectangles.
Formula:
Floor Area (sq ft) = Length (ft) × Width (ft)Pro Tip: For L-shaped rooms, break the room into two rectangles, calculate each separately, then add them together.
Common Measurement Mistakes
❌ Don't Do This
- • Measuring diagonally instead of along walls
- • Forgetting to subtract doors and windows
- • Using floor area for paint calculations
- • Rounding measurements too early
- • Mixing feet and inches without converting
✓ Do This Instead
- • Measure each wall at baseboard level
- • Measure and subtract all openings
- • Calculate wall area for paint needs
- • Keep measurements in inches until final calculation
- • Convert everything to feet before multiplying
Skip the Math - Use Our Calculator
Input your measurements and let our calculator handle the formulas. Includes automatic waste factors and material quantities.
Go to Interior Paint Calculator →Quick Reference: Room Sizes
| Room Type | Typical Size | Wall Area (approx) |
|---|---|---|
| Bedroom | 12' × 12' | 384 sq ft |
| Living Room | 16' × 20' | 576 sq ft |
| Bathroom | 8' × 10' | 288 sq ft |
| Kitchen | 10' × 12' | 352 sq ft |
*Assumes 8-foot ceilings and subtracts 20% for openings