Calculate square footage for a rectangle, circle, triangle, or multi-room layout — with an optional cost estimate.
Choose a shape, enter your measurements, and click Calculate
This free square footage calculator works out the area of a room or space in square feet, supporting rectangles, circles, triangles, and multi-room (L-shaped or combined) layouts — plus an optional cost-per-square-foot field so you can see an estimated total project cost alongside the area itself.
Choose the shape that best matches your space. For a rectangle, the calculator multiplies length by width. For a circle, it uses Area = π × radius², where radius is half your entered diameter. For a triangle, it uses Area = ½ × base × height. For an L-shaped or multi-section room, add each rectangular section as its own row under "Multiple Rooms" and the calculator sums every section's area into one total. If you enter a cost per square foot, that total is multiplied by your area to estimate a total project cost.
Homeowners planning flooring, carpet, paint, or renovation projects; real estate agents and buyers sanity-checking a listed square footage; landscapers and contractors estimating material costs by area; and anyone who needs a fast, no-fuss area calculation for an irregular or multi-section space.
The exact formula used for each shape
The most common room shape — simple length × width multiplication, assuming square corners.
Uses the radius, not the diameter, in the formula — a common source of error if the diameter is used directly without halving it first.
Splitting an irregular space into rectangles and summing their areas is the standard approach used by flooring and construction estimators.
From choosing a shape to reading your total area and cost
Select Rectangle, Circle, Triangle, or Multiple Rooms depending on your space.
Fill in the length/width, diameter, or base/height fields for your chosen shape — add rows for each section under Multiple Rooms.
Enter a cost per square foot for flooring, paint, or another material to get an estimated total cost.
See your total square footage, the equivalent in square meters, and (if entered) the estimated total cost.
A circular patio and an L-shaped multi-room layout
A main room of 12 ft × 10 ft plus an attached nook of 8 ft × 6 ft.
Where an accurate area calculation matters
Calculate the exact area before ordering flooring, carpet, or tile materials.
Work out wall or ceiling area to estimate paint or wallpaper quantities.
Sanity-check a listing's stated square footage against your own room-by-room measurements.
Calculate irregular yard, garden bed, or patio areas for sod, mulch, or paver estimates.
Break a multi-room renovation into sections and get one combined total area.
Use the cost-per-square-foot field to get a fast total cost estimate for any area-priced material.
Estimate a space's square footage for rent-per-square-foot comparisons.
What this square footage calculator does well, and where it has boundaries
Get a more accurate square footage figure
Summary: This square footage calculator handles rectangles, circles, triangles, and multi-room layouts in one tool, with an optional cost-per-square-foot estimate — free, instant, and entirely client-side. Pair it with the Tile / Flooring Calculator or Paint Calculator to turn your area into a material shopping list.
Common questions about calculating square footage
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