Square Footage Calculator: Area for Rooms, Lots and Irregular Shapes

1. Pick a shape from the dropdown: rectangle, square, circle, triangle, trapezoid, ellipse or L-shape.
2. Enter the dimensions in the fields that apply to your shape. Unused fields can stay blank.
3. Choose the unit your measurements are in. The calculator converts everything to feet internally.
4. Read the area in square feet, square meters, square yards and acres.
5. Optionally enter a cost per sq ft to get a total price estimate.

Square footage is the area of a surface measured in square feet. One square foot is a square that measures one foot on each side, which equals 144 square inches or about 0.0929 square meters.

Knowing the square footage of a room, lot or irregular space is essential for flooring, painting, landscaping, real estate listings and construction estimates. This calculator gives you the area from simple dimensions so you do not have to work out the geometry by hand.

For construction material estimates, see the construction calculators hub.

The calculator applies standard Euclidean geometry formulas to the dimensions you enter, after converting them to feet.

The result is always shown in square feet, then converted to square meters (multiply by 0.09290304), square yards (divide by 9) and acres (divide by 43,560). If you enter a cost per square foot, the calculator multiplies it by the total area for a quick price estimate.

Rectangle 20 by 15 Feet

Area = 20 x 15 = 300 sq ft. That equals 300 x 0.09290304 = 27.87 sq m and 300 / 9 = 33.33 sq yd.

Circle with a 10-Foot Diameter

Radius = 5 ft. Area = pi x 5 x 5 = 78.54 sq ft.

Triangle with Base 12, Height 8

Area = 0.5 x 12 x 8 = 48 sq ft.

Trapezoid with Bases 10 and 14, Height 6

Area = 0.5 x (10 + 14) x 6 = 0.5 x 24 x 6 = 72 sq ft.

L-Shape: 20 X 10 Plus 8 X 5

Area = (20 x 10) + (8 x 5) = 200 + 40 = 240 sq ft.

All conversions are exact based on the international foot definition (1 ft = 0.3048 m exactly).

The calculator accepts inputs in feet, inches, meters, centimeters or yards and converts internally before computing the area in square feet.

Most rooms are close to rectangular, so measure the longest wall for length and the adjacent wall for width. If the room has alcoves, closets or bump-outs, break it into rectangles, calculate each, and add them together using the L-shape or multiple passes.

L-Shaped Rooms

Split the floor into two rectangles. Measure each section and enter the dimensions as L1 x W1 and L2 x W2. The calculator sums the two areas.

Rooms with Angles

For triangular cutoffs or bump-outs, measure the base and height of the triangular section, calculate its area separately, then add or subtract from the main rectangle.

Outdoor Lots

Larger lots may be trapezoidal. Measure the two parallel sides and the perpendicular distance between them. For very large areas the result also shows acres.

Flooring

Whether you are laying tile, carpet or hardwood, the area in square feet tells you how much material to buy. Add 10 percent for waste and cuts.

Painting

Wall area determines how much paint you need. Measure each wall (length x height) and add them together, then subtract window and door openings.

Landscaping

Calculate the square footage of a garden bed, patio or lawn section to order the right amount of gravel, mulch or seed.

Real Estate

Home listings are priced per square foot. Knowing the exact area helps you compare properties and estimate market value.

Construction

Framing, drywall, insulation and roofing all start with an area calculation. Accurate square footage prevents over-ordering and waste.

1. Measure Twice

Always double-check your dimensions before entering them. A small error in length or width can compound into a large area error.

2. Use the Same Unit

Make sure all your measurements are in the same unit. The calculator handles the conversion, but mixing units in a single field will give a wrong result.

3. Account for Obstacles

Subtract the area of built-in cabinets, columns, stairwells or other permanent fixtures if they reduce the usable floor space.

4. Round Up for Materials

When ordering flooring, paint or other materials, round up to the next whole unit and add a waste percentage (typically 10 percent).

5. Check at Multiple Points

Walls are not always perfectly parallel. Measure width at two or three points along the room and use the largest value.

The math behind this calculator is exact Euclidean geometry. The formulas return the precise area for the shape and dimensions you enter.

Knowing your square footage lets you estimate project costs quickly. Multiply the area by the price per square foot for the material or service.

These ranges are typical guidelines and vary by region, material quality and labor. Enter your own price per sq ft in the calculator for an estimate specific to your project.

Multiply the length by the width of a rectangular space. For a 20 by 15 foot room the area is 300 square feet. For other shapes use the matching formula: circle, triangle, trapezoid, ellipse or L-shape.

A 12 by 12 foot room is 144 square feet. That is also exactly 1 square yard multiplied by 16, or about 13.38 square meters.

Multiply the square footage by 0.09290304. For example 300 sq ft times 0.09290304 equals about 27.87 sq m.

One acre equals 43,560 square feet. A quarter-acre lot is 10,890 sq ft.

Break the room into rectangles, triangles or other standard shapes. Calculate each area separately and add them together. The L-shape option does this for two rectangles automatically.

Use the formula A = pi times the radius squared. For a circle with a 10-foot diameter the radius is 5 feet and the area is about 78.54 sq ft.

You need at least 300 sq ft of flooring material, plus 10 percent extra for waste and cuts, so about 330 sq ft total.

Add the two parallel bases, multiply by the height and divide by two. Bases of 10 and 14 feet with a 6-foot height give 72 sq ft.

Yes. Select meters from the unit dropdown and the calculator converts your dimensions to feet internally, then shows the area in both sq ft and sq m.

Enter your price per square foot in the optional cost field. The calculator multiplies the area by that rate to give a total estimate.

• Euclidean Geometry: Area Formulas (Wolfram MathWorld; standard area formulas for plane figures).
• NIST: International Foot Definition (National Institute of Standards and Technology; 1 ft = 0.3048 m exactly).
• US Survey and Land Measurement (NOAA National Geodetic Survey; acre, hectare and land area references).