Sq Footage

How Sq Footage Works

Rectangle: A = l × w | Circle: A = πr² | L-Shape: A = (l₁×w₁) + (l₂×w₂)

A

Area — Total square footage of the space.

l / w

Length & Width — Dimensions of a rectangular section in feet or meters.

r

Radius — Distance from center to edge of a circular area.

π

Pi — Mathematical constant ≈ 3.14159, used for circular area.

How to Use

1. Select the shape of the area: rectangle, circle, or L-shape.
2. Enter the required dimensions for the chosen shape.
3. Choose your input unit (feet or meters).
4. Optionally add a waste factor (10% is standard for flooring) and a price per square foot for a cost estimate.

Quick Reference

Understanding the Result

Worked Examples

Frequently Asked Questions

Why do I need a waste factor?

Materials like flooring, tile, and carpet rarely fit perfectly into a space without cutting. The waste factor accounts for off-cuts, pattern matching, mistakes, and future repairs. For standard rectangular rooms, 5% is usually enough. For diagonal installations, L-shapes, or rooms with many corners, 10-15% is recommended.

How do I convert square feet to square meters?

Multiply square feet by 0.092903 to get square meters. Conversely, multiply square meters by 10.7639 to get square feet. This calculator does both conversions automatically.

What is an L-shaped room and how is it measured?

An L-shaped room is any space that forms an "L" configuration — two rectangular sections joined at a right angle. To calculate its area, split it into two rectangles, calculate each area separately using length × width, and add them together.

How much flooring do I need for a 12×12 room?

A 12×12 ft room has 144 sq ft of floor area. With a 10% waste factor, you should order 144 × 1.10 = 158.4 sq ft of material. It's always better to round up to account for measuring errors and unexpected cuts.

How do I measure square footage for carpet or flooring on stairs?

Stairs require a different measurement approach. Each stair tread (horizontal surface) plus the riser (vertical face) is measured together. Measure the tread width and depth, and the riser height, all in inches. For each stair, the total square footage = (tread depth + riser height) × tread width / 144. Multiply by the number of stairs. For example, 13 stairs with a 10-inch tread, 7-inch riser, and 36-inch width: each stair covers (10 + 7) × 36 / 144 = 4.25 sq ft, and 13 stairs total 55.25 sq ft. Add a landing area (if present) separately. For carpet, add 3-4 inches to each measurement for trimming and pattern matching. For LVP (luxury vinyl plank) or hardwood on stairs, each tread is typically a single piece cut to size, so you need one plank or board per tread plus the riser trim pieces. For bullnose treads (rounded front edge), measure from the back of the tread to the farthest point of the nose. Stair nose molding (transition pieces) is ordered separately by linear foot equal to the total width of all stairs.

Pro Tips

• →Measure twice, order once. Measure each wall independently rather than assuming a room is a perfect rectangle. Walls are rarely perfectly parallel — measure at both ends and use the average. For flooring, measure the room at its widest and longest points. A 1-inch measurement error in a 20-foot room translates to 1.7 sq ft of error.
• →For flooring installations, always buy all your material from the same dye lot or production run. Boxes of flooring from different production batches can have subtle color variations that are invisible in the store but glaringly obvious once installed side by side. Write down the dye lot number from the box and confirm all boxes match.
• →Before measuring, sketch the room on paper with all dimensions and note any alcoves, bay windows, doorways, closets, and built-in features. Include the swing of each door — a door that opens into the room requires clearance that may affect where flooring can end. This sketch will be invaluable when laying out your flooring pattern and planning cuts.
• →Acclimate your flooring material in the room where it will be installed for at least 48-72 hours before installation. This allows the material to adjust to the room's temperature and humidity, preventing gaps or buckling after installation. Stack boxes flat with spacers between them for airflow. The room should be at normal living temperature (65-75°F) and humidity (35-55%) during acclimation.
• →When calculating for paint (wall area, not floor area), use the formula: wall area = (perimeter × ceiling height) — (door area + window area). One gallon of quality paint covers approximately 350-400 sq ft of wall area in one coat. A 12×12 room with 8 ft ceilings has a perimeter of 48 ft and a wall area of 48 × 8 = 384 sq ft — almost exactly one gallon per coat. Always apply two coats for even coverage and color depth.
• →For carpet, the roll width (typically 12 ft) determines the minimum width of your order regardless of room dimensions. A 10×10 ft room requires a 12×10 ft piece of carpet = 120 sq ft (13.3 sq yards), not 100 sq ft. The extra 2-foot strip is waste. Always order carpet by the square yard (divide square feet by 9) and confirm the roll width with your installer.

Limitations to Know

• •This calculator handles rectangles, circles, and L-shaped rooms only. For rooms with more than two rectangular sections, curved walls, bay windows, hexagonal rooms, or irregular polygons with more than 4 sides, divide the floor plan into simpler shapes, calculate each separately, and sum the results. Octagonal rooms, for example, can be treated as a square plus four triangles at the corners.
• •The waste factor is an estimate based on typical installations. For diagonal flooring installations (running at 45 degrees to the walls), increase the waste factor by 5-10% above the selected value. For herringbone, chevron, or other intricate parquet patterns, waste can reach 20-30%. For large-format tile (12×24 inches or larger), waste increases because each broken or miscut tile wastes more square footage.
• •The calculator does not account for material-specific ordering units. Flooring is sold by the box (typically 20-25 sq ft per box for laminate, 15-22 sq ft for hardwood, 12-15 sq ft for luxury vinyl plank). Tile is sold by the box (typically 10-15 sq ft per box). Carpet is sold by the square yard (divide sq ft by 9). Always round up to the nearest full box — partial boxes are rarely returnable after the job is done.
• •Square footage calculations for real estate purposes are governed by ANSI Z765 standards in the US, which specify that only finished, above-grade living space with a ceiling height of at least 7 feet counts toward the listed square footage. Garages, unfinished basements, and attics with less than 7 feet of headroom do not count. This calculator measures total floor area and does not distinguish between finished and unfinished space.

Sources

• Square Foot
• Area