Square Feet of a Rectangle Calculator
How it Works
01Enter Dimensions
Input length and width of your rectangle
02Pick Your Units
Choose ft, m, in, yd or cm per dimension
03Instant Area
Get square footage with one click
04Full Conversions
See m², in², yd² and perimeter instantly
How to Calculate the Square Footage of a Rectangle
Whether you're laying flooring, planning a garden bed, ordering carpet, or calculating paint coverage, the first question is always the same: how many square feet is this space? For a rectangle — the most common shape in home improvement and construction — the answer is simple. This calculator does that math instantly, with one added power: you can mix units freely. Length in feet, width in metres? No problem — it converts everything automatically before calculating.
Square footage is the standard unit for floor area in the United States, used for everything from real estate listings to flooring quotes to permit applications. It's calculated by multiplying length by width — but only when both are in the same unit. Most calculators force you to convert first. This one handles the conversion internally so you can enter dimensions in whatever unit you measured them.
💡 Mixed Unit Support
Each dimension has its own unit selector — choose from feet, meters, inches, yards, or centimetres independently. A room that's 4.5 meters long and 12 feet wide can be entered exactly as measured. The calculator converts both to feet before multiplying, then also returns the result in m², in², and yd² for complete flexibility.
Enter your length and width (in any supported unit), click Calculate, and see your result in square feet instantly — alongside the equivalent area in square metres, square inches, and square yards, plus the perimeter of the rectangle.
How to Use the Square Feet Calculator
The Formula: Length × Width
Area = Length × Width. For a 10 ft × 5 ft rectangle: Area = 50 sq ft. The formula is the same for any rectangle or square — the only variable is ensuring both dimensions use consistent units before multiplying. This calculator handles that conversion step automatically.
Before multiplying, each dimension is converted to feet: 1 meter = 3.28084 ft, 1 inch = 0.0833 ft (1/12), 1 yard = 3 ft, 1 cm = 0.0328 ft (1/30.48). These are exact conversion factors used internationally. After converting to feet, the multiplication happens in a single consistent unit, preventing errors from mixed-unit arithmetic.
Square Meters: sq ft × 0.092903. Square Inches: sq ft × 144. Square Yards: sq ft ÷ 9. Perimeter: 2 × (length + width) in feet. All derived values are calculated from the same converted inputs, ensuring consistency across all output units.
Common Use Cases and Example Calculations
Here are typical real-world measurements and their resulting square footages:
| Scenario | Length | Width | Area (sq ft) |
|---|---|---|---|
| Living Room | 15 ft | 12 ft | 180 sq ft |
| Bedroom | 4.5 m | 3.6 m | 174.4 sq ft |
| Garden Bed | 8 ft | 3 ft | 24 sq ft |
| Office (mixed units) | 5 m | 14 ft | 229.7 sq ft |
Who Uses a Square Footage Calculator?
Technical Reference
Key Takeaways
Square footage is one of the most universally needed calculations — and one of the most error-prone when done manually with mixed units. This calculator eliminates the unit-conversion step that causes most mistakes, giving you an accurate result regardless of whether your tape measure shows feet, your architectural plan shows meters, or your tile supplier quotes in centimetres.
For any rectangular space, the result is exact: length in feet × width in feet. The unit conversions this tool applies are based on the internationally defined, exact values used in engineering and construction worldwide.
Need the area of non-rectangular shapes? Visit our Area Calculator for circles, triangles, trapezoids, and more. Explore more in our Math & Science Calculators Collection.
Frequently Asked Questions
How do I calculate square feet of a rectangle?
Multiply the length by the width, where both are measured in feet. Area (sq ft) = Length (ft) × Width (ft). For a room that is 12 feet long and 10 feet wide: Area = 12 × 10 = 120 sq ft. If your measurements are in other units, convert to feet first (1 meter = 3.28084 ft, 1 inch = 0.0833 ft, 1 yard = 3 ft) — or use this calculator which does the conversion automatically.
Can I use different units for length and width?
Yes — this calculator supports mixed units. Each input field has its own independent unit selector. You can enter length in meters and width in feet, for example, and the calculator converts both to feet before multiplying. This is especially useful when you have measurements from different sources (a tape measure in feet and an architectural plan in metric) and don't want to manually convert.
How many square feet is a 10x10 room?
A 10 × 10 foot room is 100 square feet. This is a standard reference size often used to estimate carpet or flooring needs. In metric: 100 sq ft = 9.29 m². A typical bedroom is 120–150 sq ft; a living room is 200–350 sq ft; a small apartment studio is 300–400 sq ft.
What's the difference between square feet and linear feet?
Square feet is a unit of area — it describes a two-dimensional space (length × width). Linear feet is a unit of length — it's simply feet measured in a straight line. Flooring and carpet are sold in square feet (area). Molding, lumber, and fencing are typically sold in linear feet (length). Don't confuse the two when ordering materials — buying 100 linear feet of flooring boards is very different from covering 100 square feet of floor.
How do I convert square feet to square meters?
Multiply square feet by 0.092903. For example: 150 sq ft × 0.092903 = 13.94 m². To go the other way (m² to sq ft), multiply by 10.7639. This calculator shows both conversions automatically in the results.
How much flooring do I need for a room in square feet?
Calculate the room's square footage (length × width), then add a waste factor:
- Straight-lay tile or plank: Add 10%
- Diagonal-lay tile: Add 15%
- Carpet: Add 10–15% (carpets must account for roll width and seam placement)
For a 200 sq ft room with straight-lay tile: order 200 × 1.10 = 220 sq ft of tile to cover cuts and breakage.
Author Spotlight
The ToolsACE Team
Our math tools team calculates rectangle area using A = length × width — accepting input in feet, meters, inches, yards, or centimeters with automatic unit conversion, and outputting the area in square feet, square meters, and square inches simultaneously.