How to Calculate Square Feet

This calculator works out the area of a rectangular space in square feet when you enter its length and width. You can mix feet and inches (for example, 12 ft 6 in by 8 ft 3 in), and the result is given in square feet and also in square meters. The formula is simple: multiply length by width, but the calculator saves you from converting inches to feet first.

Formula

The area in square feet is found by multiplying the length by the width, where each dimension is expressed in feet. If you have inches as well, convert them to feet by dividing by 12.

Area (sq ft) = (Length in feet + Length in inches / 12) × (Width in feet + Width in inches / 12)

Variables:

• Length in feet (ft) – the longer side of the rectangle
• Length in inches (in) – the extra inches beyond the whole feet
• Width in feet (ft) – the shorter side
• Width in inches (in) – the extra inches beyond the whole feet

To convert to square meters, multiply the square feet result by 0.092903 (since 1 sq ft = 0.092903 m²).

Worked Example

Using the default values: length = 12 ft 6 in, width = 8 ft 3 in.

1. Convert length to feet: 12 + 6/12 = 12 + 0.5 = 12.5 ft
2. Convert width to feet: 8 + 3/12 = 8 + 0.25 = 8.25 ft
3. Multiply: 12.5 × 8.25 = 103.125 sq ft
4. Round to two decimals: 103.13 sq ft
5. Convert to square meters: 103.125 × 0.092903 = 9.58 m² (rounded)

The calculator shows 103.13 sq ft and 9.58 m².

When to Use This

You need square footage whenever you are buying flooring, tile, carpet, paint, or sod, or when you are comparing room sizes. Real estate listings often quote square footage, and landlords may use it to price rent. Contractors estimate materials and labor based on square footage. It is also used in construction for drywall, roofing, and concrete. Even for simple tasks like choosing an area rug, knowing the floor area helps you avoid buying something too large or too small.

The calculation assumes the space is a rectangle or can be split into rectangles. For L-shaped rooms, divide them into two rectangles, calculate each area, and add them together. For circles or triangles, you need different formulas.

Common Mistakes

• Mixing units without converting – Multiplying feet by inches directly gives a nonsense number. Always convert inches to feet first.
• Forgetting to divide inches by 12 – A common error is to write 6 inches as 6 instead of 0.5 ft.
• Rounding too early – If you round each dimension to the nearest foot, you lose accuracy. Keep at least two decimal places until the final answer.
• Using the wrong side as length – For a rectangle, it does not matter which side you call length, but you must use the two perpendicular sides, not the diagonal.
• Ignoring irregular shapes – A room that is not a perfect rectangle needs to be split into rectangles; otherwise, you overestimate or underestimate.
• Confusing square feet with cubic feet – Square feet is two-dimensional (area), cubic feet is three-dimensional (volume). For volume, you multiply length × width × height.

Tips

• Measure to the nearest inch for most home projects; that is usually enough accuracy.
• For large areas, measure twice to avoid errors.
• When buying materials, add 5–10% extra for waste, cuts, and mistakes.
• If you have a tape measure that only shows feet and inches, write down the inches separately.
• For oddly shaped rooms, draw a sketch and divide it into rectangles. Label each rectangle with its dimensions.
• Use the metric result if you are purchasing materials that are sold in square meters.

Troubleshooting

Your result seems too large or too small. Check that you entered the dimensions in the correct fields. A common mix-up is entering inches in the feet field. For example, 5 ft 6 in should be 5 in the feet field and 6 in the inches field, not 5.6 ft.

The calculator returns an error. Make sure all fields have numbers. If you leave a field blank, the formula cannot compute. Enter 0 for inches if you have no extra inches.

You get a negative number. This happens if you enter a negative length or width. Dimensions cannot be negative; enter positive numbers only.

Your measurements are in meters or yards, not feet. Convert them to feet first: 1 meter = 3.28084 ft, 1 yard = 3 ft. Then use the calculator.

You are measuring an L-shaped room. Split it into two rectangles, calculate each area separately, then add them. You can use the calculator twice and sum the results.

Frequently Asked Questions

How many square feet is a 10×10 room? A room that is 10 feet by 10 feet has an area of 100 square feet (10 × 10 = 100).

How do I convert square feet to square meters? Multiply the square footage by 0.092903. For example, 500 sq ft × 0.092903 = 46.45 m².

What is the difference between square feet and feet squared? They are the same thing. “Square feet” and “feet squared” both mean an area measured in square feet, e.g., 100 sq ft = 100 ft².

Can I calculate square feet from inches? Yes. Convert inches to feet by dividing by 12, then multiply length by width. For instance, 120 inches × 60 inches = 10 ft × 5 ft = 50 sq ft.

How do I measure a room with sloped ceilings? For flooring, measure the floor area only. For wall area or paint, measure the wall’s height at the tallest point and the width, then subtract windows and doors. For carpet on stairs, measure each step’s tread and riser separately.

Does the calculator work for triangular rooms? No, this calculator is for rectangles. For a triangle, use the formula: Area = 0.5 × base × height. Measure the base and the perpendicular height, then multiply and divide by 2.

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in len_ft | Length (feet) | ft | 12 | 0
in len_in | Length (inches) | in | 6 | 0
in wid_ft | Width (feet) | ft | 8 | 0
in wid_in | Width (inches) | in | 3 | 0
out sqft | Square Feet | sq ft | (len_ft + len_in/12) * (wid_ft + wid_in/12) | 2
out sqm | Square Meters | m² | ((len_ft + len_in/12) * (wid_ft + wid_in/12)) * 0.092903 | 2