Square Footage Calculator
Add rectangular rooms in feet, then read the combined square footage and the same area in acres.
Smart Tips
• Each room is a rectangle: length times width, in feet.
• Add a row for every room, then read one total.
• A room that is 180 feet by 242 feet is exactly 1 acre.
• A zero width adds nothing.
• Circles and triangles stay on the area calculator.
The Formula
square feet = sum of length × width; acres = square feet ÷ 43,560
L × WOne rectangular room, in feet.
sumEvery room added together.
43,560Square feet in one acre, exactly.
0A zero side contributes zero area.
12 × 10 plus 15 × 12 is 300 square feet, which is 300 ÷ 43,560 acres.
Key Insights
Rooms, not shapes
This page adds rectangles. Named shapes are the area calculator.
One total
The hero number is the sum. Acres is that sum divided by 43,560.
Exact acre
43,560 square feet is one acre. 180 by 242 feet is that number.
Empty side
A width of 0 does not change the total.
Frequently Asked Questions
Multiply the length in feet by the width in feet. A 12 by 10 room is 120 square feet. Add another room on a new row. The total is the sum.
43,560. The acre figure on this page is the square-foot total divided by 43,560. A single room of 180 feet by 242 feet is exactly 1 acre.
No. Those shapes are on the area calculator. This page is only rectangular rooms and the acre conversion of their sum.
That room contributes 0 square feet. The other rooms still add up.
Yes. Enter feet. If you measured inches, convert before you type, or use the length converter and come back.
Each room is length times width in feet, and the rooms are summed. Acres divide that total by 43,560. NIST Special Publication 811 states that 1 acre = 43,560 square feet exactly. www.nist.gov/pml/special-publication-811/nist-guide-si-appendix-b-conversion-factors
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Add rectangular rooms to total the area
Note:Acres use 1 acre = 43,560 square feet, the exact relationship in NIST SP 811. Only rectangles are added.