How to Calculate Square Footage: Every Room Shape
Calculate square footage for rectangles, triangles, circles, and irregular rooms. Step-by-step formulas with examples, plus a free square footage calculator.
Square Footage Calculator — Direct Answer
To calculate square footage: multiply length × width in feet. A 12×14 ft room is 168 sq ft. For irregular rooms, split into rectangles, triangles, and circles, calculate each separately, then add. Add 5–10% for waste when ordering flooring, paint, or tile.
→ Calculate square footage with our free square footage calculator
How to Calculate Square Footage
Every area formula starts with length × width. The only difference is how you handle non-rectangular shapes.
Rectangle: Length × Width
Triangle: (Base × Height) ÷ 2
Circle: π × Radius²
Irregular: Sum of all sub-shapes
Where:
- π = 3.14159
- Radius = diameter ÷ 2
- All measurements in feet
How to measure a rectangular room
Measure length and width at the widest points. Include closets and alcoves.
Example: 12 ft × 14 ft room = 168 sq ft
For L-shaped rooms, split into two rectangles:
- Rectangle A: 12 × 10 = 120 sq ft
- Rectangle B: 6 × 8 = 48 sq ft
- Total = 168 sq ft
How to measure a triangular area
For triangular closets or accent walls:
Area = (Base × Height) ÷ 2
Example: 8 ft base × 6 ft height = 24 sq ft
For a right triangle at the end of a rectangular room, this is common in attic conversions.
How to measure a circular area
For round dining areas, columns, or planters:
Area = π × r²
Example: 10 ft diameter room:
- Radius = 5 ft
- Area = 3.14 × 25 = 78.5 sq ft
How to apply the formula to real rooms
Example: 20 × 15 ft living room with a 6×6 ft bay window
- Main room = 20 × 15 = 300 sq ft
- Bay window (half circle) = (π × 3²) ÷ 2 = 14.1 sq ft
- Total = 314 sq ft
Square Footage by Room Type
Common room sizes
| Room | Typical Size | Sq Ft |
|---|---|---|
| Bedroom (small) | 10 × 10 | 100 |
| Bedroom (large) | 14 × 16 | 224 |
| Bathroom (full) | 5 × 8 | 40 |
| Bathroom (master) | 8 × 12 | 96 |
| Kitchen | 10 × 12 | 120 |
| Living room | 16 × 20 | 320 |
| Dining room | 12 × 14 | 168 |
| Garage (1-car) | 12 × 22 | 264 |
| Garage (2-car) | 22 × 22 | 484 |
Material yield per square foot
| Material | Coverage | Notes |
|---|---|---|
| Paint (1 gallon) | 350–400 sq ft | 1 coat |
| Tile (case) | 10–20 sq ft | Add 10% waste |
| Hardwood (case) | 20–25 sq ft | Add 5% waste |
| Carpet (roll) | 12-ft wide | Add 10% waste |
| Drywall (sheet) | 32 sq ft | 4×8 ft sheet |
| Concrete (yard) | 81 sq ft at 4" | Volume-based |
Common Square Footage Mistakes
Mistake 1: Measuring in inches
Multiply inches together gives square inches. Divide by 144 to convert to sq ft.
Fix: Measure in feet from the start. Or convert: 12" × 12" = 144 sq in = 1 sq ft.
Mistake 2: Forgetting irregular shapes
L-shaped rooms measured as one rectangle underestimate by 15–25%.
Fix: Split into rectangles. Measure each. Add totals.
Mistake 3: Not adding waste
Ordering exactly the calculated square footage guarantees shortages.
Fix: Add 5% for solid materials, 10% for tile and patterned flooring, 15% for diagonal installation.
Square Footage vs Square Yards
When to use square feet
- Paint
- Flooring (most)
- Room size
- Wall area
- Roof area
When to use square yards
- Carpet (always)
- Concrete (as cubic yards)
- Topsoil (as cubic yards)
- Landscape fabric
Conversion
1 square yard = 9 square feet
1 square foot = 0.111 square yards
Example: 500 sq ft = 55.6 sq yd
Square Footage Calculator FAQ
How do I calculate square footage?
Multiply length × width in feet. For irregular rooms, split into rectangles, calculate each, then add.
How many square feet is a 12×12 room?
144 square feet. Multiply 12 × 12.
How do I calculate square footage of an irregular room?
Split the room into rectangles and triangles. Calculate each separately. Add all totals.
How do I convert inches to square feet?
Multiply the two inch measurements, then divide by 144. For example, 24" × 24" = 576 ÷ 144 = 4 sq ft.
How much square footage does a gallon of paint cover?
350–400 sq ft per gallon for one coat on smooth surfaces. Two coats needed for most jobs.
Next Steps for Your Square Footage Project
- Square Footage Calculator — Room, wall, ceiling
- Area Calculator — Rectangles, triangles, circles
- Flooring Calculator — Boxes and overage
- Paint Calculator — Gallons per room
- Flooring Estimator Guide — Box counts
Last updated October 2026. Verify measurements twice before ordering materials.