Square Footage Calculator
Calculate square footage from length and width, plus total cost.
Try an example
180 sq ft
About this calculator
What Is Square Footage?
Square footage is the area of a flat surface measured in square feet: how many 1-foot-by-1-foot squares would cover it. It is the number you use to size a room, price flooring, order paint or tile, compare apartments, estimate a lot or work out heating and cooling needs. This square footage calculator finds the area of common shapes — rectangles, circles, triangles, trapezoids, parallelograms, rings and sectors — and lets you total up complex spaces by splitting them into simple pieces.
Area Formulas for Common Shapes
- Rectangle: length × width.
- Circle: π × radius².
- Triangle: ½ × base × height (or Heron's formula from the three sides).
- Trapezoid: ½ × (base 1 + base 2) × height.
- Parallelogram: base × height.
- Ring: π × (outer radius² − inner radius²).
- Sector: ½ × radius² × angle (in radians).
For an L-shaped room, split it into two rectangles, find each area and add the results; for a room with a cut-out, subtract the area you do not need.
Worked Example
A 12 ft × 15 ft room is 180 square feet — at $5/sq ft, that comes to $900 in total material cost.
Useful Conversions
- 1 acre = 43,560 square feet
- 1 square yard = 9 square feet
- 1 square meter ≈ 10.76 square feet
- 1 square inch ≈ 0.00694 square feet
Using Square Footage to Estimate Cost and Materials
Many jobs are priced per square foot. Professional painters often base quotes on the size of a property, and even if you paint yourself, area tells you how much paint to buy — a gallon typically covers roughly 350–400 square feet of wall for one coat. Flooring, tile, carpet, sod, roofing, insulation and fencing are also sold or priced by area. Total cost covers more than the material itself: tools, preparation, waste and labor all add up. Allow roughly 5%–10% extra for cuts and mistakes.
Measuring Tips
- Measure each wall at the longest point, and note alcoves and bump-outs.
- Take every measurement in the same unit before you multiply.
- For wall area, multiply the perimeter by the ceiling height, then subtract doors and windows.
For pouring slabs, use the Concrete Calculator, and for shapes with unknown sides use the Triangle Calculator and the Circle Calculator.
Worked example
A 12 ft × 15 ft room is 180 square feet — at $5/sq ft, that's $900 in total material cost.
Frequently asked questions
How do I measure an irregularly shaped room?
Split it into rectangles, calculate each section's square footage separately, then add them together — this calculator handles one rectangle at a time.
Should I round up when ordering flooring or paint?
Yes — most materials are sold with some allowance needed for cuts, waste, and pattern matching, so ordering 5-10% more than the exact square footage is standard practice.
