Free project calculator

Square Foot Calculator – Calculate Room, Floor, Wall & Project Area

Use the Square Foot Calculator – Calculate Room, Floor, Wall & Project Area to get a quick estimate, review the formula, and plan your project with clearer numbers.

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Square Foot Calculator – Calculate Room, Floor, Wall & Project Area

Room / Floor Area Calculator

Calculate square feet for a room, floor, patio, garage, deck, or basic project area.

Multiple Room Calculator

Add bedrooms, living rooms, kitchens, bathrooms, garages, and other areas to get total square footage.

Wall Square Footage Calculator

Useful for paint, wallpaper, drywall, paneling, and accent wall projects.

Flooring Calculator

Estimate flooring square feet, waste, boxes, material cost, labor cost, and total cost.

Most flooring projects need 5% to 15% extra material for cuts, mistakes, and future repairs.

Paint Square Footage Calculator

Estimate paintable wall area, gallons needed, and paint cost.

Many interior paints cover about 250 to 400 square feet per gallon depending on surface texture, color, and paint type.

Tile Square Footage Calculator

Estimate tile count, extra tile with waste, and project cost.

Carpet Square Footage Calculator

Estimate carpet in square feet and square yards, including waste and cost.

Lawn / Yard Calculator

Estimate lawn square footage, acres, sod cost, seed bags, and seed cost.

Unit Converter

Convert square feet to square yards, square meters, acres, and more.

Cost Estimator

Estimate material, labor, waste, sales tax, and total project cost.

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How to use Square Foot Calculator – Calculate Room, Floor, Wall & Project Area

  1. Pick the tab that matches your job: room, walls, flooring, paint, tile, carpet, lawn, conversion, or cost.
  2. Enter the measurements and confirm the unit before calculating.
  3. Add practical details such as waste, box coverage, coats, tile size, or labor cost when needed.
  4. Use the result summary and formula steps to check your numbers before buying materials.

Practical tip: Measure twice. A small measuring error can become expensive across a whole floor or several walls.

Room length and width square-foot measurement example
A 12 ft × 10 ft room has an area of 120 square feet.

Core formula

How square footage is calculated

For a rectangle or square, multiply the length by the width after both measurements are in the same unit. A room measuring 12 feet by 10 feet is 120 sq ft. For an odd-shaped room, split the floor into smaller rectangles, calculate each part, and add the results.

RectangleLength × width
TriangleBase × height ÷ 2
Circleπ × radius²
WallsWidth × height × wall count
Flooring square footage with ten percent waste example
Adding 10% waste changes 120 sq ft of floor area to 132 sq ft of material.

Planning flooring, tile, carpet, and paint

Flooring and tile usually need extra material for cuts and damaged pieces. Five percent may be enough for a simple straight layout, while 10% is a sensible starting point for many rooms. Diagonal patterns, closets, stairs, and irregular shapes can require more.

For walls, multiply width by height and add the wall areas together. Subtract doors and windows when you need the paintable area. Paint coverage varies by product and surface, so compare the calculator estimate with the coverage printed on the can.

Carpet may be priced in square feet or square yards. Divide square feet by 9 to convert to square yards.

Square feet conversion chart

ConversionResult
1 square yard9 square feet
1 square meter10.7639 square feet
1 acre43,560 square feet
100 square feet11.11 square yards
500 square feet55.56 square yards
1,000 square feet111.11 square yards

Common room sizes

Room sizeArea
10 × 10 ft100 sq ft
10 × 12 ft120 sq ft
12 × 12 ft144 sq ft
12 × 15 ft180 sq ft
15 × 20 ft300 sq ft
20 × 20 ft400 sq ft
24 × 24 ft garage576 sq ft

Before ordering materials

  • Check whether the product is sold by square foot, square yard, box, gallon, roll, tile, pallet, or bag.
  • Round up to complete boxes, gallons, tiles, sod rolls, or seed bags.
  • Keep a small amount of matching flooring or tile for future repairs.
  • For a large or expensive job, ask the installer to confirm the final measurements.

Helpful answers

Square Foot Calculator – Calculate Room, Floor, Wall & Project Area FAQs

A square foot is an area measurement equal to a square that is 1 foot long and 1 foot wide.

Multiply length by width. For example, 12 feet by 10 feet equals 120 square feet.

A 10x10 room is 100 square feet.

A 12x12 room is 144 square feet.

A 20x20 room is 400 square feet.

Multiply the room length by the room width, then add 5% to 15% extra for waste.

Many projects use 5% to 10% extra. Irregular rooms, diagonal layouts, closets, and stairs may need 15% or more.

Multiply wall width by wall height. For multiple walls, calculate each wall and add them together. Subtract doors and windows if needed.

Many paints cover about 250 to 400 square feet per gallon, but coverage depends on the paint, surface, color, and number of coats.

One square yard equals 9 square feet.

One acre equals 43,560 square feet.

Yes. Enter the yard length and width to estimate lawn square footage, sod cost, and seed coverage.

Yes. Enter the room size, tile size, and waste percentage to estimate how many tiles are needed.

Yes. The tool shows both square feet and square yards, which is helpful because carpet may be priced by either unit.

Yes, the calculator is free to use and works directly in your browser.

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