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Room Square Footage Calculator

Use this room square footage calculator to find the area of a room from its length and width in feet and inches, with a second rectangle to add for an L-shaped room.

  • Instant answer as you type
  • Nothing you type is sent anywhere
  • Worked example with clear steps

Your measurements

ft
in
Fractions are fine. Blank is 0. The limit of 1,200 is ours.
ft
in
Fractions are fine. Blank is 0. The limit of 1,200 is ours.
Another part to add, or an area to take away (optional)

For an L-shaped room or an alcove, measure it as a second rectangle. Take away the area of a closet or a bump-out.

ft
in
ft
in
ft²

Result

Calculated live
Area 14.5 x 12.25 ft
177.63 ft²
Square yards 9 ft² in a yard
19.74 yd²
Square meters 1 ft² is 0.09290304 m²
16.5 m²
Length as feet feet + inches / 12
14.5 ft
Width as feet feet + inches / 12
12.25 ft

Based on NIST SP 811 NIST Handbook 44, Appendix C Home Innovation, ANSI Z765 Full list of sources

Assumptions and constants

You can change

Fixed values (exact definitions and references)

These are exact definitions and cannot be edited.

Inches in a foot Reference [1]

12 in per ft

The foot is 0.3048 m and the inch is 0.0254 m, both exact, so 12 inches make a foot.

Square feet in a square yard Reference [1]

9 ft² per yd²

3 ft × 3 ft. NIST gives the yard as exactly 0.9144 m and the foot as exactly 0.3048 m.

How to use the room square footage calculator

  1. Enter the Length, feet and Length, inches of the room.
  2. Enter the Width, feet and Width, inches.
  3. For an L-shaped room, open Another part to add, or an area to take away (optional) and enter the added part.
  4. Read Area and Square yards.
  5. Use Copy result or Print, and check the area against your plan.

How to calculate the square footage of a room

The area of a rectangular room is its length times its width, with both in feet. For an L-shaped room, find the area of each rectangle and add them. Square yards = square feet / 9, because a square yard is 9 square feet. [2] Square meters = square feet x 0.09290304, the factor NIST lists for a square foot. [1]

Worked example

A room 14 ft 6 in long and 12 ft 3 in wide. 6 in is 6 / 12 = 0.5 ft, so the length is 14.5 ft. 3 in is 3 / 12 = 0.25 ft, so the width is 12.25 ft. 14.5 x 12.25 = 177.63 square feet. Divided by 9 that is 19.74 square yards, and times 0.09290304 it is 16.5 square meters.

Room: length 14.5 ft, width 12.25 ft A room seen from above, a rectangle a little longer than it is wide. Its length, 14.5 ft, is marked under it and its width, 12.25 ft, along the right side. From above Length 14.5 ft Width 12.25 ft
Drawn to scale for a room 14 ft 6 in long and 12 ft 3 in wide, seen from above. The sides are shown in feet: 14.5 and 12.25.

How do I calculate square footage with feet and inches?

Turn each side into feet: the feet plus the inches divided by 12. A foot is 12 inches. [1] Then multiply the length in feet by the width in feet. Enter the feet and the inches in the boxes above and the calculator does both steps.

Inches to decimal feet

Each inch is one twelfth of a foot. The table gives the decimal for 1 to 11 inches.

Inches as decimal feet
Inches Feet (decimal)
1 0.0833
2 0.1667
3 0.25
4 0.3333
5 0.4167
6 0.5
7 0.5833
8 0.6667
9 0.75
10 0.8333
11 0.9167

Is room square footage measured inside or outside the walls?

Home Innovation Research Labs says the ANSI Z765 standard covers the calculation and reporting of above-grade and below-grade square footage in single-family houses, and does not cover room dimensions. [3]

We found no source that sets how a single room is measured. For flooring or paint, measure the floor you will cover, from wall to wall inside the room.

Common mistakes and limits

  • Typing inches as decimals. 6 inches is 0.5 feet, not 6 hundredths. Use the inches boxes and the calculator converts.
  • Forgetting the second part of an L-shape. Open the section for another part and enter its length and width.
  • What this tool does not cover: walls, ceilings, stairs and the area of a whole house, which has its own rules.

Frequently asked questions

How do I calculate the square footage of an L-shaped room?

Split the room into rectangles, find the area of each, and add them. Enter the main rectangle, then open Another part to add, or an area to take away (optional) for the second one. For a closet or a bump-out, enter its area under Area to take away.

Why do you divide by 144 to get square feet?

NIST Handbook 44 lists 1 square foot as 144 square inches, because a foot is 12 inches and 12 x 12 = 144. So an area in square inches, divided by 144, is square feet. [2]

Can you calculate square footage with inches?

Yes. Turn each side into feet: feet plus inches divided by 12. Then multiply the two. For 14 ft 6 in, that is 14 + 6 / 12 = 14.5 ft.

How do I find the square footage of a house?

Find the area of each room and add them. For a whole house, with floors, walls and what counts, see the square footage calculator, which covers a house.

How do I find the square footage of a triangle?

A triangle is its base times its height, divided by 2. The square footage calculator has a triangle option, and this page measures rooms made of rectangles.

Sources and references

  1. National Institute of Standards and Technology (NIST). NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically (SP 811, accessed November 2026). Used for: the inch and foot relationship and the square meters in a square foot.
  2. National Institute of Standards and Technology (NIST). Handbook 44, Appendix C, General Tables of Units of Measurement (2026, accessed November 2026). Used for: the 144 square inches in a square foot and the 9 square feet in a square yard.
  3. Home Innovation Research Labs. Square Footage Method for Calculating, ANSI Z765, frequently asked questions (accessed November 2026). Used for: that the ANSI Z765 standard does not cover room dimensions.

How we use sources: methodology.

Estimates only. Confirm quantities with your supplier. See the disclaimer. Found a wrong result? Report an error.