Square Footage Calculator

Knowing the exact square footage of a space determines how much flooring to buy, what a property is worth, and whether your furniture will fit. A 10% miscalculation on a 2,000 sq ft project can mean $600 of wasted hardwood or a failed appraisal.

The calculator above handles any shape – rectangles, circles, triangles, and L-shaped rooms – and converts results into square meters, acres, or hectares instantly.

What Is Square Footage?

Square footage is a measure of area expressed in square feet (sq ft or ft²). One square foot equals a square that is 1 foot long and 1 foot wide – 144 square inches, or approximately 0.0929 square meters.

In the United States, square footage is the standard unit for measuring floor area in homes, commercial spaces, and land parcels. The UK and Canada also use it alongside metric units, while most other countries rely on square meters.

How to Calculate Square Footage?

The formula depends on the shape of the area you are measuring. Below are the most common scenarios.

Rectangle or Square

This is the simplest and most frequent calculation:

Area = Length × Width

A bedroom that is 14 feet long and 12 feet wide: 14 × 12 = 168 sq ft.

Triangle

For triangular spaces such as bay windows or angled ceilings:

Area = ½ × Base × Height

A triangular alcove with a 6-foot base and 4-foot height: 0.5 × 6 × 4 = 12 sq ft.

Circle

For circular areas like round patios or curved staircases:

Area = π × Radius² (where π ≈ 3.14159)

A circular patio with a 10-foot radius: 3.14159 × 10² = 314.16 sq ft.

Trapezoid

For irregular quadrilaterals like angled lots:

Area = ½ × (Side A + Side B) × Height

A lot with parallel sides of 40 ft and 60 ft and a height of 30 ft: 0.5 × (40 + 60) × 30 = 1,500 sq ft.

How to Measure Irregular or L-Shaped Rooms?

Most rooms are not perfect rectangles. The standard approach is to break the shape into simpler parts:

1. Sketch the room on paper, noting all wall lengths.
2. Divide the sketch into rectangles, triangles, or both.
3. Measure each section’s dimensions.
4. Calculate the area of each section using the formulas above.
5. Add all sections together for the total square footage.

Example: an L-shaped living room splits into a 15×12 rectangle (180 sq ft) and a 8×10 rectangle (80 sq ft). Total: 260 sq ft.

Square Footage to Square Meters and Other Units

A 2,500 sq ft home equals approximately 232.3 sq meters (2,500 × 0.0929).

Common Uses for Square Footage Calculations

• Flooring and tile – add 10–15% extra for cuts and waste
• Paint – one gallon covers roughly 350–400 sq ft of wall surface
• HVAC sizing – contractors estimate 1 ton of cooling per 400–600 sq ft
• Property valuation – price per square foot is the primary metric in real estate comparisons
• Property tax – assessed value often scales with gross living area
• Rent – commercial leases quote rates per square foot per year

How to Measure a Room Accurately?

1. Use a laser distance measurer for precision – tape measures introduce sag and parallax errors.
2. Measure wall to wall at floor level, excluding baseboard thickness.
3. Take measurements at two points along each wall – rooms are rarely perfectly square.
4. Record the larger of the two measurements for each dimension.
5. For vaulted ceilings, measure the floor area separately from wall area.

ANSI Z765 Standard for Measuring Square Footage

The American National Standards Institute (ANSI) publishes Z765, the most widely referenced standard for calculating residential square footage in the US. Key rules under ANSI:

• Measure to the exterior face of outside walls – wall thickness is included
• Stairs count as the area of the stair tread on each level
• Open lofts and balconies are excluded from gross living area
• Finished basements are listed separately from above-grade area
• Spaces with ceiling height below 5 feet are excluded
• Spaces with ceiling height between 5 and 7 feet are included at 50% of their floor area

This article provides general guidance. For real estate transactions or tax assessments, consult a licensed appraiser and refer to local regulations, which may differ from ANSI standards.

Quick Reference: Common Room Sizes

For fast results on any shape, the square footage calculator at the top of this page handles the math – enter your dimensions and get the area in multiple units at once.