Square Feet Calculator
Use this tool to quickly calculate square footage for flooring, paint planning, tile, carpet, sod, and more.
Enter two non-overlapping rectangles that together form your L-shape.
How to figure square feet quickly
Square footage is one of the most useful measurements in home improvement and real estate. Whether you are buying flooring, ordering carpet, estimating paint, or comparing apartments, knowing how to calculate square feet gives you cleaner numbers and better decisions. The calculator above helps you figure square feet instantly for common shapes.
At a basic level, square feet means area: how much flat surface a space covers. One square foot is a square that is 1 foot by 1 foot. If your room is 10 feet by 10 feet, the area is 100 square feet.
Square footage formulas by shape
Rectangle or square
This is the most common scenario for bedrooms, living rooms, and open floor areas.
- Formula: Length × Width
- Example: 18 ft × 12 ft = 216 sq ft
Triangle
Useful for angled sections, some yards, or irregular design features.
- Formula: (Base × Height) ÷ 2
- Example: (14 × 10) ÷ 2 = 70 sq ft
Circle
Great for round patios, rugs, and decorative spaces.
- Formula: π × radius²
- Example: 3.1416 × 8² = 201.06 sq ft
L-shaped rooms
Break the room into two rectangles, calculate each, and add the results.
- Formula: (L1 × W1) + (L2 × W2)
- Example: (15 × 10) + (6 × 4) = 174 sq ft
Step-by-step measuring method
- Measure each side in feet (use decimals when needed, like 12.5 ft).
- Choose the shape that best fits your space.
- Enter dimensions into the calculator.
- Add a waste percentage for cuts, breakage, and errors.
- Use optional cost and box coverage fields to estimate materials and budget.
Why waste allowance matters
Many people calculate net area correctly but still under-order materials. For flooring or tile, you typically need extra for trimming around walls, closet corners, and doorways. Patterned materials can require even more.
- Simple rectangular rooms: 5% to 8%
- Average residential rooms: 10%
- Complex layouts and patterns: 12% to 15%+
This calculator automatically applies your waste percentage to produce a realistic total purchase area.
Common mistakes when calculating square footage
- Mixing inches and feet without converting first
- Forgetting to split irregular rooms into simpler shapes
- Ignoring waste factor
- Rounding too early and stacking rounding errors
- Not double-checking measurements before buying materials
Practical example: flooring estimate
Suppose your room is 19.2 ft by 13.5 ft. Net area is 259.2 sq ft. Add 10% waste and you need 285.12 sq ft. If each flooring box covers 23.3 sq ft, you need 13 boxes (always round up). If material costs $4.20/sq ft, your rough material cost is about $1,197.50 before tax and installation.
Frequently asked questions
How do I calculate square feet from inches?
Convert inches to feet first by dividing by 12. Then multiply length by width in feet.
Is square feet the same as linear feet?
No. Square feet measures area. Linear feet measures length only. They are used for different purposes.
Can this calculator help with paint?
Yes for wall or ceiling area estimates. Just remember paint also depends on coats, texture, and product coverage rates.
What if my room has many angles?
Break the layout into rectangles, triangles, and circles as needed, then add all sections. For very complex spaces, sketch your room and label each measurement before calculating.
Final tip
If you want accurate project planning, measure twice and calculate once. A reliable square feet estimate saves money, avoids delays, and makes purchasing much easier.