How do I calculate square footage of a room?

Multiply the length by the width in feet. A 12 by 15 foot room is 180 square feet.

How many square feet in an acre?

43,560 square feet per acre. A football field (excluding end zones) is about 48,000 sq ft or 1.1 acres.

How do I calculate square footage of a circle?

Use pi times radius squared. For a 15 ft diameter circle: 3.14159 times 7.5 squared equals 176.7 sq ft.

What is the square footage of a 12x12 room?

144 square feet. This is a standard bedroom size in most residential construction.

How do I convert square feet to square yards?

Divide square feet by 9. For example, 270 sq ft equals 30 square yards. Carpet is often priced per square yard.

How accurate do my measurements need to be?

Measure to the nearest inch for most home projects. This gives accuracy within 1 to 2 percent, which is adequate for material ordering.

UtilitySquare Footage Calculator

Square Footage Calculator

Q: How do I convert square feet to square meters?

Multiply square feet by 0.0929. For example, 200 sq ft equals 18.58 square meters.

Q: How do I measure an L-shaped room?

Divide it into two rectangles. Measure each one (length times width), calculate the area of each, and add them together.

Calculate area for rooms, yards, patios, circles, triangles, and odd shapes.

Area Details

Shape

Rooms, slabs, lawns, walls, and patios.

Length (ft)

Width (ft)

Ready to calculate

Enter dimensions to find the area.

Last updated June 9, 2026 by our expert review team

Shape Formula Reference

Shape	Use it for	Formula
Rectangle	Rooms, slabs, lawns, walls, and patios.	length x width
Triangle	Triangular beds, gables, and odd corners.	base x height / 2
Circle	Round patios, pools, rugs, and tables.	pi x radius squared
Trapezoid	Tapered yards, beds, and rooms.	(top + bottom) x height / 2
L-shape	Split an odd room into two rectangles.	rectangle 1 + rectangle 2

For multiple rooms or an odd plan, calculate each simple shape first, then add the areas before choosing a material calculator.

Expert Contributors

Creator

Hawkin

Certified Cost & Estimating Professional

Hawkin

Certified Cost & Estimating Professional

AACE-certified estimator working with 20+ insulation companies including the two largest franchises in America.

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Expert Review

Ehsan Ghazanfari

Licensed Structural Engineer

Ehsan Ghazanfari

Licensed Structural Engineer

FISE-certified structural engineer with 11+ years designing bridges, retaining walls, and foundations. MSc from Aalto University.

See full profile

Updated June 2026

How we verify our calculators

Square Footage Measurement Guide

Measure the surface, choose the closest shape, split odd rooms into simple pieces, then convert units only after the math is done.

For real estate square footage, use the measurement method required by the lender, appraiser, or listing rules. Project material takeoffs may use a different surface.

Use Area for Material Planning

Flooring

Add 5-10% waste for straight rooms, more for angles.

Paint

Use wall area, subtract large openings, then estimate gallons.

Tile

Add cuts and layout waste after measuring the surface.

Mulch or concrete

Area is only step one. Depth turns area into volume.

Pro Tips

Use one unit for every measurement in a shape. Mixing feet, inches, and meters is the fastest way to miss an order.

Split odd rooms into rectangles, triangles, or circles. Calculate each piece, then add the areas.

For material orders, measure the actual work surface. Wall paint, flooring, mulch, and concrete all use different surfaces.

Use the sq ft to linear ft calculator when board width or roll width matters.

After the area is known, use the flooring calculator for boxes, waste, and project cost.

How the Calculator Works

The calculator computes area in the selected unit, then converts the result to square feet, square meters, square yards, acres, and square inches.

Rectangle

length x width

Circle

pi x (diameter / 2)^2

Odd rooms

area 1 + area 2 + area 3

Quick Reference

1 sq yd: 9 sq ft
1 sq meter: 10.7639 sq ft
1 acre: 43,560 sq ft
12 x 12 room: 144 sq ft
20 x 24 garage: 480 sq ft
15 ft circle: 176.7 sq ft

Common Square Footage Examples

Small bedroom

10 x 10 ft rectangle

100 sq ft

Quick flooring, paint, or rug check.

Average bedroom

12 x 12 ft rectangle

144 sq ft

Common room-size reference.

Living room

15 x 20 ft rectangle

300 sq ft

Same as the default calculator result.

Two-car garage

20 x 24 ft rectangle

480 sq ft

Useful for flooring, storage, and slab planning.

Round patio

15 ft diameter circle

176.7 sq ft

Circle area uses radius, not diameter.

Square Footage Calculator FAQ

How do I calculate square footage?

Multiply length by width when the shape is a rectangle. A 12 x 15 room is 180 square feet.

How do I measure an L-shaped room?

Split it into two rectangles, calculate each rectangle, then add the two areas.

How do I convert square feet to square meters?

Multiply square feet by 0.092903. The calculator does this automatically.

How many square feet are in an acre?

One acre is 43,560 square feet.

Do I use inside or outside measurements?

For DIY materials, measure the work surface. For real estate, follow the required appraisal or listing standard.

How accurate should I measure?

Nearest inch is usually enough for DIY material estimates. Add the material-specific waste allowance in the next calculator.

Measurement Mistakes

Mixing units

Convert inches or centimeters before multiplying dimensions.

Using diameter as radius

Circle area uses radius squared. Diameter must be divided by 2 first.

Treating every odd room as a rectangle

Split notches and alcoves into separate shapes, then add the areas.

Using real estate area for materials

Listing square footage and project surface area can be different measurements.

Important Disclaimer

These estimates are for planning purposes only. Actual costs vary by location, material availability, and project complexity. Always get at least 3 local quotes. This calculator does not replace professional advice.