Square Footage Calculator
Free square footage calculator. Compute area for rectangular, triangular, or circular rooms — total sqft from length, width, or radius for any space.
Quick answer
Rectangular area = length × width. Triangular area = ½ × base × height. Circular area = π × radius². The calculator handles mixed-shape rooms by adding individual sections together.
Square Footage Calculator
How it works
Multiplies length × width to give you the area in square feet. For irregular shapes, divide the room into rectangles, calculate each one, and add them together. The same formula works in any unit — square inches, square meters — as long as both measurements use the same unit.
When to use it
Use this when buying flooring, carpet, paint, wallpaper, tile, or any product sold by area. Also useful for property listings, room-size comparisons, and figuring out how much furniture will fit.
Common mistakes
Measuring at the baseboard instead of wall-to-wall, or forgetting to subtract closets and built-ins when measuring a room for flooring. For most products, buy 10% extra to cover waste, cuts, and mistakes.
How the square footage calculator works
For rectangles, the math is length × width. For triangles, ½ × base × height (where height is measured perpendicular to base). For circles, π × radius². The calculator supports adding multiple shapes for L-shaped rooms or houses with bays and angled walls — sum each shape's area, total at the end. All inputs accept feet, inches, or mixed units; output is in square feet by default with conversions to square meters.
When to use it
Sizing flooring, paint, or wallpaper purchases. Calculating rental rates by sqft. Computing property tax assessments. Sizing HVAC for a room (typically 20 BTU per sqft for basic sizing). Estimating concrete or sod for outdoor areas. Sanity-checking listing-sheet square footage against actual measurements before signing a lease or purchase.
Common mistakes
- Mixing inches and feet without converting. A 12 × 10 foot room is 120 sqft. A 12 × 10 inch room is less than 1 sqft. Always check unit consistency.
- Including unfinished basement or attic in 'living area.' Real estate definitions vary. Most agencies exclude unheated, finished-but-low-ceiling, or below-grade areas from the headline 'living square footage.'
- Treating wall thickness as zero. For interior carpet calculation, ignoring walls adds 1-2% per partition. For exterior measurements, add 6-12 inches per wall to convert exterior dimensions to interior usable space.
Frequently asked questions
How do I calculate square footage?
For a rectangular room, multiply length by width — both in the same units (feet × feet). For irregular rooms, break into rectangles and triangles, calculate each, and sum. The calculator above handles common shape combinations.
Does the calculator handle L-shaped or irregular rooms?
Yes. Add multiple shape sections — the calculator sums their areas. For complex shapes, break the floor plan into rectangles and triangles, measure each, and add.
Should I include closets and hallways?
Depends on your purpose. For flooring, paint, and HVAC sizing, include all enclosed areas under the same conditions. For real estate listings, follow ANSI Z765 standard for the U.S. — generally exclude unheated areas and stairwells.