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Geometry Basics

Rectangle Area Calculator

Use this for rectangular rooms, walls, panels, slabs, yards, and project areas.

Last updated: July 2026

Unit system Switch between U.S. customary and metric units. Your choice is remembered on other calculators.

Rectangle dimensions

Enter the length and width in the units you know. The result will show both square feet and square meters.

Visual guide

Which measurement goes where?

Use the long horizontal side as length and the side-to-side dimension as width.

ft
ft
Advanced settings
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Buying and sizing notes

Square footage measurement tips

Square footage searches are usually simple, but mistakes happen when rooms have closets, jogs, alcoves, stairs, or multiple rectangles. Use this calculator as the base measurement, then round for the material you are buying.

Break up odd shapes

For L-shaped rooms, closets, or floor plans, calculate each rectangle separately and add them together.

Keep units consistent

Do not multiply feet by inches. Convert measurements first, or use the unit switch where available.

Add overage for materials

Flooring, tile, roofing, paint, and other materials usually need waste or coverage rounding beyond pure square footage.

Use plans carefully

Floor plan square footage is only as accurate as the scale and dimensions shown. Field measurements are better before buying materials.

How to use this estimate

What this includes

  • Length
  • width
  • optional overage
  • square feet and square meters

What it does not include

  • Irregular curves
  • rooms measured from plans without scale verification
  • waste rules for specific products

Common mistakes

  • Forgetting closets or alcoves
  • Measuring only one section of an irregular room
  • Multiplying inches as if they were feet
  • Not rounding up for full boxes, rolls, sheets, or bags

Quick questions

How do I calculate square footage?

Measure length and width in the same unit, multiply length by width, then add any overage needed for the material or project.

How do I calculate square footage for an odd-shaped room?

Break the room into smaller rectangles, calculate each area separately, then add the pieces together.

Should I include closets?

Yes, include closets, alcoves, and other connected floor areas if you need material for those spaces.

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