Square Footage Calculator
Calculate the area in square feet for rooms, lots, and various shapes. Convert between area units.
A square footage calculator computes the area of rooms, lots, or irregularly shaped spaces from length and width measurements.
Examples
Room measurement
Circular patio
Frequently Asked Questions
How many square feet in an acre?
How do I measure an irregular room?
Quick Tips
- •For L-shaped rooms, calculate each rectangle separately and add them together.
- •When measuring in inches, the calculator converts to feet automatically.
- •Use the quantity field for repeating areas like identical tiles or rooms.
A square footage calculator computes the area of rooms, lots, or irregularly shaped spaces from length and width measurements.
How to Use This Calculator
Select the shape of the area, choose your measurement unit, enter the dimensions, and optionally set a quantity if you have multiple identical areas. The calculator converts all inputs to square feet.
Understanding the Formula
Rectangle: Area = Length x Width. Circle: Area = pi x Radius^2. Triangle: Area = 0.5 x Base x Height. Irregular quadrilateral: Brahmagupta's formula sqrt((s-a)(s-b)(s-c)(s-d)) where s is the semi-perimeter.
Examples
Room measurement
A 12 ft x 15 ft room = 180 sq ft. This is about 16.7 square meters.
Circular patio
A circular patio with 8 ft radius: Area = pi x 64 = 201.06 sq ft.
Frequently Asked Questions
How many square feet in an acre?
1 acre = 43,560 square feet. The calculator shows the acre equivalent for any area.
How do I measure an irregular room?
Break the room into rectangles and triangles, calculate each separately, then add the areas together. For four-sided irregular shapes, enter the four side lengths.
Assumptions & Limitations
- Irregular quadrilateral calculations use Brahmagupta's formula, which assumes a cyclic quadrilateral and may overestimate non-cyclic shapes.
- Measurements should be taken from wall to wall; built-in fixtures and closets may reduce usable area.
- Unit conversions use standard factors; rounding may introduce minor discrepancies on very large areas.