Square Footage Calculator

Calculate area for any room or lot shape — rectangle, triangle, circle, L-shape, or trapezoid — with automatic unit conversions.

Select Shape

Length (ft)

Width (ft)

Formula: Length × Width

Cost per sqft (optional, $/sqft)

Enter to calculate total material or project cost.

Area

300.00 sqft

33.33 sq yd · 27.87m²

Square Feet	300.00 sqft
Square Yards	33.33 sq yd
Square Meters	27.87 m²

Standard area formulas. Rectangle: L × W. Triangle: ½ × base × height. Circle: π × r². L-shape: total bounding rectangle minus the cutout rectangle. Trapezoid: ½ × (side1 + side2) × height. 1 acre = 43,560 sqft. 1 sqft = 0.0929 m². Acres displayed only for areas ≥ 1,000 sqft.

Frequently Asked Questions

How do I calculate square footage of an irregular room?

Break the room into simple rectangles, calculate each one separately, then add the areas together. For most L-shaped or T-shaped rooms, this works perfectly — just make sure your measurements don't overlap. Use the L-Shape mode above for the most common irregular room type.

How many square feet is an acre?

One acre is exactly 43,560 square feet. A standard American football field (including end zones) is about 1.32 acres or roughly 57,600 sqft. A quarter-acre residential lot — common in suburban subdivisions — is 10,890 sqft.

How do I convert square feet to square yards?

Divide by 9. One square yard = 9 square feet (because 1 yard = 3 feet, and 3 × 3 = 9). This matters most for carpet and flooring sold by the square yard. A 12×15 room is 180 sqft or 20 square yards.

What's the easiest way to measure a room?

For rectangular rooms, measure the longest length wall to wall, then the widest width wall to wall. Measure at floor level. For irregular shapes, sketch it out on paper first and break it into rectangles. A laser distance measurer makes this faster and more accurate than a tape measure for larger spaces.

How the square footage calculator works

The square footage calculator finds the area of a space and converts it into every unit you are likely to need. Pick one of five shapes and enter its dimensions in feet; the tool computes the area with the standard geometry formula for that shape.

A rectangle is length multiplied by width. A triangle is one-half times the base times the height. A circle is pi times the radius squared; you can enter either the radius or the diameter, and the calculator halves the diameter for you. An L-shape is the overall bounding rectangle minus a rectangular cutout removed from one corner, which handles most irregular rooms. A trapezoid is one-half times the sum of the two parallel sides, multiplied by the height.

Once it has the square footage, the calculator converts it automatically. Square yards are the area divided by 9, because one yard is 3 feet and 3 times 3 equals 9 square feet per square yard. Square meters are the area multiplied by 0.0929. Acres are the area divided by 43,560, and are displayed only when the area reaches 1,000 square feet or more, since acres are not meaningful for a single room. If you enter an optional price per square foot, the tool also multiplies it by the area to estimate material or project cost. The calculator is bilingual, with an English and Spanish toggle.

Worked example: a rectangular room 20 feet long and 15 feet wide is 20 times 15, or 300 square feet. Dividing by 9 gives about 33.33 square yards, the unit carpet is often sold in, and multiplying by 0.0929 gives about 27.87 square meters. Because 300 square feet is under the 1,000 square foot threshold, no acreage is shown. Enter a price such as $12.50 per square foot and the estimate becomes 300 times $12.50, or $3,750. For an irregular room, break it into rectangles or use the L-shape mode and add the pieces together.

Frequently Asked Questions

What shapes can this calculator handle?

It supports five shapes: rectangle (length times width), triangle (one-half times base times height), circle (pi times radius squared, entered as radius or diameter), L-shape (the overall bounding rectangle minus a corner cutout), and trapezoid (one-half times the two parallel sides times the height).

How do I calculate the square footage of an L-shaped room?

Use L-shape mode. Enter the overall bounding rectangle, then the cutout rectangle removed from one corner. The calculator subtracts the cutout area from the overall area. For a 30 by 20 room with a 12 by 10 cutout, that is 600 minus 120, or 480 square feet.

How does it convert between units?

Square yards are the square footage divided by 9, since a yard is 3 feet and 3 times 3 is 9. Square meters are the square footage multiplied by 0.0929. Acres are the square footage divided by 43,560, and are shown only when the area reaches 1,000 square feet or more.

Can it estimate project cost?

Yes. Enter an optional price per square foot and the calculator multiplies it by the total area to give a project or material cost. Leave it blank if you only need the area and unit conversions.