Total Square Feet Calculator: How to Find Area

This calculator works out the total square footage of a rectangular room or space. You enter the length and width in feet (or inches, and it converts for you), and it returns the area in square feet, plus the same area in square yards and square meters for convenience.

Formula

The total square footage of a rectangle is simply its length multiplied by its width:

Area (sq ft) = Length (ft) × Width (ft)

• Length – the longer side of the rectangle, measured in feet (ft).
• Width – the shorter side, also in feet (ft).
• Area – the result, in square feet (sq ft).

If you measure in inches, convert to feet first by dividing by 12: ft = inches / 12. For example, 72 inches becomes 6 feet.

Worked Example

Using the default values from the calculator above: length = 12 ft, width = 10 ft.

1. Multiply length by width: 12 × 10 = 120
2. The area is 120 square feet.
3. To get square yards, divide by 9: 120 / 9 = 13.33 sq yd.
4. To get square meters, multiply by 0.092903: 120 × 0.092903 = 11.15 sq m.

The calculator shows the same result: 120.00 sq ft, 13.33 sq yd, 11.15 sq m.

When to Use a Total Square Feet Calculator

Square footage is the standard unit for real estate listings, flooring orders, paint estimates, and HVAC sizing in the United States, Canada, and the UK. You’ll need it when:

• Buying or selling a home – the listed square footage affects the price.
• Ordering flooring, tile, or carpet – you need the area to know how much material to buy.
• Estimating paint – one gallon of paint typically covers about 350 sq ft of wall (but that’s for walls, not floors).
• Planning a garden or lawn – to buy sod or fertilizer.

For a simple rectangle (most rooms, apartments, or lots), this calculator is all you need. For L-shaped rooms, split the shape into two rectangles, calculate each, and add them together. For a triangle, use 0.5 × base × height.

How to Read the Result

The number you get is the floor area – the two-dimensional space inside the walls. It does not include wall thickness, and it assumes the room is a perfect rectangle. If your space has bay windows, closets, or irregular nooks, the real area will be slightly different.

When buying materials, always add a waste factor: 10% for flooring, 15% for tile (due to cutting and breakage). For example, a 120 sq ft room needs about 132 sq ft of flooring material.

Common Mistakes and How to Avoid Them

• Mixing units – If you measure one side in feet and the other in inches, you’ll get a wrong answer. Convert everything to the same unit first.
• Forgetting to convert inches – If you enter 10 ft and 120 inches, the calculator treats 120 as feet, giving 1,200 sq ft instead of the real 100 sq ft. Use the inch conversion or measure in feet.
• Rounding too early – If you round 12.5 ft to 12 ft, you lose 0.5 ft of accuracy. Keep decimals until the end.
• Confusing square feet with feet – Square feet measure area, feet measure length. A 10 ft × 10 ft room is 100 sq ft, not 10 sq ft.

Limitations of the Formula

This formula only works for rectangles. For circles, use π × r² (r = radius). For triangles, use 0.5 × base × height. For irregular shapes, break them into rectangles and triangles, calculate each, and sum them.

Also, the calculator gives you the gross area – the entire floor space. In real estate, “living area” often excludes garages, porches, and unfinished basements. Check local guidelines if you’re using this for a listing.

Frequently Asked Questions

How do I calculate square feet from inches?

Divide each measurement in inches by 12 to get feet, then multiply. For example, a 120-inch by 96-inch room is 10 ft × 8 ft = 80 sq ft.

What is the difference between square feet and square yards?

One square yard equals 9 square feet (3 ft × 3 ft). To convert sq ft to sq yd, divide by 9. To convert sq yd to sq ft, multiply by 9.

How many square feet is a 10×10 room?

A 10 ft by 10 ft room is 100 square feet. This is a common size for a small bedroom or office.

Do I need to include closets in square footage?

For your own flooring or paint estimates, yes – include closets if you’re covering the floor. For real estate listings, it depends on local rules; some areas include closets in living area, others don’t.

How do I calculate square feet for an L-shaped room?

Divide the room into two rectangles. Calculate the area of each (length × width) and add them together. For example, a 10×10 section plus a 5×5 section gives 100 + 25 = 125 sq ft.

What is the square footage of a 20×20 room?

20 ft × 20 ft = 400 square feet. That’s about the size of a two-car garage or a large studio apartment.

Related

• Hardie Siding Calculator: Square Feet
• Hectares to Acres Calculator: Quick Conversion
• Square Feet Calculator: Formula & How to Use It

in length | Length | ft | 12 | 0
in width | Width | ft | 10 | 0
out sqft | Total square feet | sq ft | length * width | 2
out sqyd | Square yards | sq yd | sqft / 9 | 2
out sqm | Square meters | sq m | sqft * 0.092903 | 2