How this is worked out
Each rectangle is its length times its width, and each circle is pi times the diameter squared over four, with pi as 355/113. Every length is rounded to the nearest sixteenth of an inch first and the areas are added up exactly, then rounded once for the answer, the way Handyman Calc does it. Take away subtracts an area, for a closet, an island or the missing corner of an L-shaped room.
A square foot is 144 square inches, a square yard is 9 square feet, a square meter is 10.764 square feet and an acre is 43,560.
On your phone, on the job site
Handyman Calc, our free app, has an area screen for rooms and circles and fourteen more calculators. It works with no signal, and it's free.
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Charts worked out with the same math:
- how many bags of concrete a slab takes
- how many sheets of drywall a room takes
- a fraction to decimal chart for inches
- how much paint a room takes
- how much mulch a bed takes
- a roof pitch chart
- how many steps a rise takes
- the diagonal that squares a frame
- board feet for common lumber
More calculators:
Frequently asked questions
How do you calculate square footage of a room?
Multiply the length by the width, both in feet. A room 12' 6" by 10' is 12.5 × 10 = 125 sq ft. Measure to the wall, not the baseboard.
How do you calculate square footage with feet and inches?
Turn the inches into a fraction of a foot first: 6 inches is 0.5 ft, 3 inches is 0.25. Or type them here as 12' 6" and the calculator does it exactly.
How do you calculate square footage of an L-shaped room?
Split it into two rectangles, work out each, and add them. Or measure the whole rectangle and take away the missing corner, which the calculator can do with Take away.
How do you calculate square footage from inches?
Multiply length by width in inches and divide by 144, the square inches in a square foot. 30 × 60 inches is 1,800 ÷ 144 = 12.5 sq ft.
How many square feet are in an acre?
43,560. A square about 208.7 ft on each side is one acre.