ContractorHandbook

How Many Square Feet Is a 20x30 Building?

Total area

600 sq ft

Twenty feet by thirty feet.

length x widthextralength, ftwidtharea x how many, plus anything odd shaped, in feet, yards and meters
Every material calculator on the site starts here, which is why this one also gives square yards and square meters. Odd shapes get broken into rectangles and added on, because a rectangle is the only shape a tape measure is honest about.

How that number is worked out

These are the figures this page was built with and every line the calculator produces from them. Change anything above and all of it moves.

  • Length20 ft
  • Width30 ft
  • How many rooms or areas this size1
  • Extra area to add0 sq ft

Total area600 sq ft

One area600 sq ft
Times 1, plus extra600 sq ft
Square yards66.67
Square meters55.74
Perimeter of one area100 ft

What else matters here

Six hundred square feet. That is a footprint rather than a room, and footprint and finished square footage are two different numbers.

A 20 by 30 building on one level is a 600 square foot home. The same footprint with a second story is 1,200. Add an unfinished basement and the listed figure does not move at all, because below grade space is reported separately from above grade living area under the usual measuring standards, no matter how nicely it is finished. Garages, attics without permanent stairs and unconditioned porches are excluded too, which is why a house can feel much larger than its listed square footage.

What this calculator assumes

  • Length times width, times how many areas are that size. For an L shaped room, split it into two rectangles and run this twice.
  • Square yards are square feet divided by nine, which is how carpet is still quoted in much of the country.

Questions people ask

How many square feet is a 20x30 building?

600 square feet of footprint, which is 66.67 square yards and 55.74 square meters.

Does a basement count toward square footage?

Not as above grade living area under the usual standards. Finished basement space is reported separately, even when it is fully finished and conditioned.

Does a garage count as square footage?

No. Garages, unconditioned porches and attics without permanent stairs are all excluded from gross living area.

Different numbers?

The square footage calculator takes any dimensions you like and hands back the same list.

Other common sizes