How do I calculate the square footage of a room?

For a rectangular room, measure the length and width in feet, then multiply them together. A 12 ft × 15 ft room is 180 square feet. For non-rectangular shapes, use the appropriate formula: triangle (0.5 × base × height), circle (π × radius²), or trapezoid (0.5 × (side1 + side2) × height).

How do I convert square feet to square meters?

Multiply square feet by 0.0929 to get square meters. For example, 500 sq ft × 0.0929 = 46.45 m². Conversely, multiply square meters by 10.7639 to get square feet.

How many square feet are in an acre?

One acre equals 43,560 square feet. To convert square feet to acres, divide by 43,560. A 10,000 sq ft lot is about 0.23 acres.

How do I calculate cost per square foot?

Divide the total cost by the total square footage. For example, if flooring costs $3,500 for a 500 sq ft room, the cost per square foot is $3,500 ÷ 500 = $7.00/sq ft. Our calculator lets you enter a $/sq ft rate and multiplies it by the total area.

Should I include closets and hallways in square footage?

For livable area (used in real estate), include all finished, heated spaces — bedrooms, living rooms, kitchens, bathrooms, closets, and hallways. Exclude garages, unfinished basements, attics, and covered porches unless they are fully finished.

Square Footage Calculator

Knowing the square footage of a room or property is essential for flooring, painting, landscaping, real estate listings, and construction budgets. This calculator handles the four most common shapes — rectangle (length times width), triangle (half base times height), circle (pi times radius squared), and trapezoid (half the sum of the parallel sides times height). Enter dimensions in feet or meters (the tool auto-converts), add as many rooms as you need, and get the combined area in both square feet and square meters. An optional cost-per-square-foot field instantly produces a total cost estimate for materials or services.

star 4.8 (534 ratings)

calendar_today Updated: April 2026

auto_awesome AI Insights AI

New

straighten Room Dimensions

Measurement Unit

Cost per Sq Ft ($) — optional

analytics Results

Total Area

0.00 sq ft

0.00 m²

Acres 0.0000

Room Breakdown

Input Values

Shape

Rectangle

Triangle

Circle

Trapezoid

Length

Width

Unit

Feet

Meters

tips_and_updates Tips

• Measure each room at its widest points and use the shape that best fits — irregular rooms can be split into multiple shapes and summed
• For L-shaped rooms, break the space into two rectangles and add both as separate rooms in the calculator
• When estimating flooring cost, add 10% extra for waste and cuts
• 1 acre = 43,560 sq ft — divide your total by 43,560 to convert to acres
• Garage and unfinished basement square footage is typically excluded from livable area in real estate listings
• Measure in the same units for all rooms — the calculator converts feet to meters and vice versa automatically

How to Use This Calculator

Select the room shape

Choose rectangle, triangle, circle, or trapezoid from the shape dropdown.

Enter dimensions

Input the required measurements (length/width, base/height, radius, or parallel sides/height) in feet or meters.

Add more rooms

Click 'Add Room' to include additional rooms. Each room can be a different shape.

Review total area

See the combined area in square feet and square meters, plus per-room breakdowns.

Estimate cost (optional)

Enter a cost per square foot to get a total cost estimate for flooring, painting, or other materials.

The Formula

Each shape uses a standard geometry formula. For a rectangle, multiply length by width. For a triangle, multiply base by height and divide by two. For a circle, multiply pi by the radius squared. For a trapezoid, add the two parallel sides, multiply by the height, and divide by two. All results are converted to square feet if the input is in meters (multiply by 10.7639).

Rectangle: A = L × W | Triangle: A = 0.5 × b × h | Circle: A = π × r² | Trapezoid: A = 0.5 × (a + b) × h

lightbulb Variables Explained

L Length of the rectangle
W Width of the rectangle
b Base of the triangle (or shorter parallel side of trapezoid)
h Height (perpendicular distance)
r Radius of the circle
a Longer parallel side of the trapezoid
A Calculated area

tips_and_updates Pro Tips

Measure each room at its widest points and use the shape that best fits — irregular rooms can be split into multiple shapes and summed

For L-shaped rooms, break the space into two rectangles and add both as separate rooms in the calculator

When estimating flooring cost, add 10% extra for waste and cuts

1 acre = 43,560 sq ft — divide your total by 43,560 to convert to acres

Garage and unfinished basement square footage is typically excluded from livable area in real estate listings

Measure in the same units for all rooms — the calculator converts feet to meters and vice versa automatically

How to Accurately Calculate Square Footage

Square footage is the standard unit of area measurement in US real estate, construction, and interior design, where accurate calculation directly affects property value, material costs, and building code compliance. The National Association of Realtors reports that pricing errors of just $10-$20 per square foot — common when square footage is miscalculated — can mean thousands of dollars of mispricing on a home sale. Calculating square footage for simple rectangular rooms is straightforward (length times width), but most real spaces involve irregular shapes that must be broken into smaller rectangles, triangles, or circles and summed. Common areas that require careful measurement include L-shaped rooms, rooms with alcoves or bay windows, multi-level spaces, and outdoor areas like decks and patios. The ANSI Z765 standard, used by appraisers nationwide, specifies that only finished, heated living space above grade counts toward gross living area — garages, unfinished basements, and covered porches are measured separately. For construction projects, accurate square footage determines quantities of flooring, paint, tile, and other materials, where even a 5% measurement error can result in costly reorders or waste.

How to measure and calculate square footage accurately

Start by measuring the longest wall (length) and the wall perpendicular to it (width) using a tape measure. For rectangular rooms, multiply length × width — a 12 ft × 15 ft room is 180 sq ft. For L-shaped or irregular rooms, break the space into simple shapes (rectangles, triangles), calculate each separately, and sum them. Always measure to the inside of the walls, not the outside. Our square footage calculator supports four shapes and lets you add unlimited rooms for a combined total.

Common cost per square foot benchmarks (2026)

Flooring installation typically costs $3–$12 per square foot depending on material (vinyl at $3–$5, hardwood at $8–$12, tile at $5–$10). Interior painting runs $1.50–$3.50 per square foot. New construction averages $150–$350 per square foot in the US depending on location and finish level. Commercial office space ranges from $15–$55 per square foot per year in rent. Plug your cost per square foot into the calculator to get an instant total estimate.

Frequently Asked Questions

Related Tools

View all Engineering View all arrow_forward

construction