Calculate square footage from a length and width in any common unit. Add a quantity for repeated areas, a waste factor, and an optional price to get the area and cost.
Usage Tip
Measure twice and to the widest points. For flooring or tile, add the waste factor here so the area you take to the store already includes the cushion.
Total = Area × number of areas
With waste = Total × (1 + waste%)
For rooms that are not simple rectangles, split them into rectangles, find each area, and add them up.
Add a waste factor for materials cut to fit — commonly about 10% for flooring and tile, more for diagonal or patterned layouts.
Materials sold by the box or sheet still need rounding up to whole units after you have the area.
How to Calculate Square Footage
Square footage is area – length times width for a rectangle. Measure both sides in feet and multiply: a 12 by 16 ft space is 192 square feet. If you measured in inches, divide each by 12 first (or enter feet-and-inches above). For non-rectangular spaces, use the matching shape or split the area into pieces and add them up.
Square Feet vs Square Yards vs Square Meters
Same area, different units – and they trip people up because the conversions are not 3 and 100, they are squared:
| From | To | Multiply by |
|---|---|---|
| Square feet | Square yards | divide by 9 |
| Square feet | Square meters | divide by 10.764 |
| Square yards | Square feet | times 9 |
| Square meters | Square feet | times 10.764 |
Carpet and concrete are often sold by the square yard; flooring and paint by the square foot; most of the world quotes square meters. The calculator shows all three together.
Area Formulas by Shape
| Shape | Area formula |
|---|---|
| Rectangle | length × width |
| Square | side × side |
| Circle | 3.1416 × radius² (radius = diameter ÷ 2) |
| Triangle | 0.5 × base × height |
| L-shaped | big rectangle − the missing corner |
| Multiple | add each area together |
Square Footage Reference Chart
| Area | Typical sq ft |
|---|---|
| Single garage | 240-400 |
| Bedroom | 120-200 |
| Living room | 200-400 |
| Kitchen | 100-250 |
And common dimensions at a glance:
| Size | Square feet |
|---|---|
| 10 × 10 | 100 |
| 12 × 12 | 144 |
| 12 × 16 | 192 |
| 20 × 20 | 400 |
Flooring & Tile Estimation
Take the square footage, add 10% for waste (10-15% for tile or diagonal layouts), then divide by the coverage of one carton or box and round up. Flooring example: 400 sq ft plus 10% is 440 sq ft; at 20 sq ft per carton that is 22 cartons. Tile example: 100 sq ft plus 15% is 115 sq ft; at 15 sq ft per box that is 8 boxes. Switch the calculator to Flooring and enter your carton coverage.
Paint Estimation
Paint covers walls, so it is based on wall area, not floor: perimeter times ceiling height times coats, divided by about 350 sq ft per gallon. Example: a room with a 60 ft perimeter and 8 ft ceilings is 480 sq ft of wall, about 3 gallons for two coats.
Real Estate Square Footage
Listed home square footage usually means finished, heated living area, measured to the outside of exterior walls (the ANSI standard). Garages, unfinished basements, and attics with low ceilings are excluded; finished basements are often listed separately. Measuring your own space rarely matches the listing exactly because of wall thickness and what counts as finished – use this for planning, not appraisal.
Landscaping & Sod
Outdoor projects use the same area math. Sod is commonly sold by the square foot, by the roll (about 10 sq ft each), or by the pallet (around 450 sq ft). Example: a 2,000 sq ft lawn needs about 5 pallets or 200 rolls, plus 5-10% for trimming around beds and curves. Mulch and gravel start from area too, then add a depth to get volume.
Multiple & Irregular Areas
For an odd shape, break it into rectangles, triangles, and circles, calculate each, and add them. The Multiple mode lets you enter several areas and totals them – handy for a whole house or a yard with separate sections. Box bay windows and angled walls to their widest points; the small error is usually within your waste allowance.
Waste Factor Recommendations
| Material | Suggested waste |
|---|---|
| Laminate / vinyl plank | 10% |
| Tile | 10-15% |
| Carpet | 10%+ |
| Sod | 5-10% |
| Paint | 5-10% |
Common Measuring Mistakes
- Multiplying inches without converting to feet first.
- Confusing square feet with square yards (off by 9x).
- Forgetting the waste allowance.
- Using floor area for paint instead of wall area.
- Missing closets, alcoves, or separate sections.
Frequently Asked Questions
How do I calculate square footage?
Multiply length by width in feet. For other shapes use the matching formula, or split the space into rectangles and add the areas.
How many square feet are in a square yard?
Nine. To convert square feet to square yards, divide by 9; to go the other way, multiply by 9.
How do I convert square feet to square meters?
Divide square feet by 10.764. One square meter is about 10.76 square feet.
How much flooring do I need for X square feet?
Add about 10% waste, then divide by the coverage of one carton and round up. The Flooring mode does this for you.
How is house square footage measured?
Listings use finished, heated living area measured to the exterior walls, excluding garages and unfinished space. Your own measurement may differ from the listed figure.
How much extra should I order for waste?
About 10% for most flooring, 10-15% for tile, and 5-10% for sod and paint.
Related Area Calculators
Note: results are planning estimates. Measurement accuracy depends on your method, and material coverage and waste vary by product and layout – always confirm against the product label and add a waste allowance. Irregular and angled areas are approximated by boxing to simple shapes. Real-estate square footage follows separate standards and may differ from a hand measurement. General DIY guidance, not a professional or appraisal-grade measurement.