Square Footage Calculator: Length x Width

This calculator works out the area of a rectangular space in square feet when you enter its length and width. Type in the length and width in feet (or inches, or meters—the calculator handles the conversion), and you get the total square footage instantly. It also shows the area in square yards and square meters, which is handy for flooring, sod, paint, or any other project that needs an area measurement.

Formula

The formula is the same one you learned in grade school: Area = Length × Width. For a rectangle, you multiply the length by the width, and the result is the area in square units. If both measurements are in feet, the area is in square feet (ft²). If you measure in inches, the area is in square inches (in²), which you can convert to square feet by dividing by 144. If you measure in meters, the area is in square meters (m²).

In the calculator above, the inputs are in feet, so the formula is simply:

Area (ft²) = Length (ft) × Width (ft)

The calculator also gives you the area in square yards (divide by 9, since 1 yd² = 9 ft²) and square meters (multiply by 0.092903, since 1 ft² = 0.092903 m²). The depth input is used only when you want to estimate volume (cubic yards or cubic feet) for materials like soil or mulch—it’s not part of the area calculation.

Worked Example

Using the default values: Length = 40 ft, Width = 25 ft.

1. Multiply: 40 × 25 = 1000 ft².
2. Convert to square yards: 1000 ÷ 9 = 111.11 yd² (rounded to two decimals).
3. Convert to square meters: 1000 × 0.092903 = 92.90 m² (rounded to two decimals).

The calculator shows the same results: 111.11 yd², 1000.0 ft², and 92.90 m². If you add a depth of 3 inches, the volume in cubic yards is (40 × 25 × 3) / 324 = 9.26 yd³, and in cubic feet it’s (40 × 25 × 3) / 12 = 250 ft³.

Why Measure Square Footage?

Square footage is the standard unit for area in the United States and Canada for real estate, construction, and home improvement. Knowing the area of a room, yard, or wall lets you buy the right amount of materials—no more guessing, no more waste. For example, if you’re installing hardwood flooring, you need to know the floor area to order the planks. If you’re laying sod, you need the lawn area to order the rolls. If you’re painting a wall, the area tells you how many gallons of paint to buy. Even when you’re just comparing the size of two apartments, square footage gives you a clear number to work with.

In many countries outside the US, area is measured in square meters. The calculator includes that conversion so you can work with either system.

How to Measure Length and Width Correctly

To get an accurate square footage, you need accurate measurements. Here’s a step-by-step approach:

• Use a tape measure that’s long enough for the space. For large rooms, a laser distance measurer is faster and more accurate.
• Measure at the widest points. For a rectangular room, measure the longest wall for length and the longest adjacent wall for width.
• Measure in feet and inches. If you get a measurement like 12 ft 6 in, convert the inches to a decimal: 6 in ÷ 12 = 0.5 ft, so 12.5 ft.
• Round to the nearest inch or centimeter. Don’t round too early—small errors compound.
• Measure twice. It’s easy to misread a tape, so double-check each dimension.

For irregular shapes, break the area into rectangles. Measure each rectangle separately, calculate its area, and add them together. That’s exactly what the calculator does for each rectangle—you just need to do it multiple times and sum the results.

Common Mistakes and How to Avoid Them

One of the most common errors is mixing units. If you measure length in feet and width in inches, the formula gives you a meaningless number. Always convert to the same unit before multiplying. For example, if a room is 10 ft long and 60 inches wide, convert 60 inches to 5 ft, then multiply: 10 × 5 = 50 ft². If you multiply 10 × 60, you get 600, which is the area in square inches, not square feet.

Another mistake is forgetting to account for obstructions like closets, columns, or bay windows. For flooring, you usually measure the open floor area, not the entire footprint. But for paint, you might need the wall area including windows and doors—though you’ll subtract those openings. Always decide what you’re measuring and stick to it.

Rounding errors can also throw off material orders. If you round each measurement to the nearest foot, you might over- or under-estimate by several square feet. Keep measurements to the nearest inch or tenth of a foot when possible.

When to Use Square Footage vs. Volume

Square footage is for flat surfaces—floors, walls, lawns, roofs. Volume is for three-dimensional spaces—how much soil, concrete, or air fits in a space. The calculator includes a depth input so you can also estimate volume in cubic yards or cubic feet. This is useful when you’re ordering fill dirt, mulch, or concrete, which are sold by the cubic yard.

For example, if you’re filling a planter box that is 6 ft long, 2 ft wide, and 1 ft deep, the volume is 6 × 2 × 1 = 12 ft³. To convert to cubic yards, divide by 27 (since 1 yd³ = 27 ft³): 12 ÷ 27 = 0.44 yd³. The calculator uses the formula (length × width × depth in inches) / 324 to get cubic yards directly, because 324 = 27 × 12 (converting inches to feet and then to yards).

How to Choose the Right Calculator

There are many square footage calculators online, but not all are created equal. Look for one that lets you choose your units (feet, inches, meters) and gives you multiple outputs (square feet, square yards, square meters). Some also allow you to add multiple areas together, which is helpful for L-shaped rooms. If you’re working on a landscaping project, you might want a calculator that also computes volume, like the one above. For real estate, you might want one that converts between square feet and acres (1 acre = 43,560 ft²). The key is to match the calculator to your project’s needs.

Real-World Examples

Here are a few scenarios where you’d use this calculator:

• Buying carpet: A bedroom is 12 ft by 14 ft. Area = 12 × 14 = 168 ft². Carpet is sold by the square foot, so you’d order at least 168 ft², plus extra for waste.
• Laying sod: A lawn is 50 ft by 30 ft. Area = 1500 ft². Sod is usually sold by the pallet, which covers a certain square footage—enter that coverage in the calculator to find out how many pallets you need.
• Painting a wall: A wall is 10 ft high and 20 ft long. Area = 200 ft². A gallon of paint covers about 350 ft², so you’d need about 0.57 gallons—round up to 1 gallon.
• Installing tile: A bathroom floor is 8 ft by 5 ft. Area = 40 ft². Tile is sold by the box, and each box covers a certain area—divide the total by the box coverage and round up.

Frequently Asked Questions

How do I calculate square footage from inches?

If you measure in inches, multiply length × width to get square inches, then divide by 144 to get square feet. For example, a countertop that is 72 inches long and 24 inches wide is 72 × 24 = 1728 in², which is 1728 ÷ 144 = 12 ft². Alternatively, convert inches to feet first (divide by 12) and then multiply.

What if my room is not a perfect rectangle?

Break the space into rectangles. Measure each rectangle separately, calculate its area, and add them together. For a L-shaped room, divide it into two rectangles. For a triangular section, use the formula (base × height) / 2. The calculator works for each rectangle—you just do it multiple times.

How many square feet is a 10×10 room?

A 10×10 room is 100 square feet (10 × 10 = 100). This is a common size for a small bedroom or office. If you’re buying flooring, you’d order a bit more than 100 ft² to account for cuts and waste.

What is the difference between square feet and square yards?

One square yard equals 9 square feet (since 1 yard = 3 feet, and 3 × 3 = 9). To convert square feet to square yards, divide by 9. For example, 100 ft² ÷ 9 = 11.11 yd². Square yards are often used for carpet and sod.

How do I calculate square meters?

If you measure in meters, multiply length × width to get square meters. If you measure in feet, multiply the square footage by 0.092903 to get square meters. For example, a room that is 200 ft² is 200 × 0.092903 = 18.58 m².

Do I need to include the depth for area?

No. Depth is only for volume calculations. Area is a two-dimensional measure—it doesn’t care about depth. If you’re ordering materials like soil or concrete, you need volume, which is area × depth. The calculator includes depth so you can get both area and volume in one go.

Related

• Land Area Calculator Online: How to Measure Any Plot
• Land Area of City Calculator: How to Estimate
• Km to Acres Calculator: Convert Quickly

in l | Length | ft | 40 | 0 | 100000
in w | Width | ft | 25 | 0 | 100000
in d | Depth | in | 3 | 0 | 120
out yd | Area | yd² | l * w / 9 | 2
out ft2 | Area | ft² | l * w | 1
out m2 | Area | m² | l * w * 0.092903 | 2