How to Calculate Square Feet
To calculate square feet, measure the length and width in feet, then multiply them: square feet = length × width. For example, a 12 ft by 15 ft room is 180 sq ft. For L-shaped rooms, houses, flooring, walls, patios or yards, split the area into simple shapes, calculate each part, then add the totals.
Quick answer
If the space is a simple rectangle, measure the length and width in feet, then multiply them. A room that is 12 feet by 15 feet is 180 square feet. If the space is not a rectangle, split it into simple shapes, calculate each area separately, then add the pieces together.
Square Feet Calculator
Use the area calculator for rectangles, triangles and circles, the feet-and-inches calculator for room measurements, or the multi-room calculator for L-shaped spaces and combined layouts.
What is square feet?
Square feet, often written as sq ft, ft², or square footage, is a unit of area. It measures surface space, not length. A single square foot is the area of a square that is exactly one foot long and one foot wide.
This matters because many real tasks start with length measurements but require area: buying flooring, estimating paint coverage, comparing apartments, measuring offices, planning furniture layouts, pricing turf, or calculating wall space.
Square feet, square footage, and sq ft: do they mean the same thing?
In everyday use, yes. Square feet is the unit. Square footage usually means the total area measured in square feet. Sq ft is the common abbreviation. If you need the area of a room, wall, floor, patio or yard, the process is the same: measure, convert units if needed, then apply the right area formula.
How to calculate square feet step by step
If the space is rectangular, the process is simple: measure the length, measure the width, convert inches to decimal feet if needed, then multiply the two measurements.
Step 1: Measure the length
Use a tape measure or laser measure and record the longest side. If the measurement includes inches, keep the inch value instead of rounding too early.
Step 2: Measure the width
Measure the second side at a right angle to the first. If the room is not rectangular, split it into smaller sections first.
Step 3: Convert inches to feet
Divide the inch portion by 12, then add it to the feet. Example: 8 inches = 8 ÷ 12 = 0.67 feet.
Step 4: Multiply length × width
Once both dimensions are in feet, multiply them. A 14.67 ft by 11.5 ft room is 168.71 square feet.
How to calculate square feet with feet and inches
If your room is 12 feet 6 inches by 10 feet 9 inches, do not multiply 12.6 by 10.9. Inches are not decimal tenths of a foot. Convert inches properly first.
So 12 feet 6 inches becomes 12 + 6 ÷ 12 = 12.5 feet. And 10 feet 9 inches becomes 10 + 9 ÷ 12 = 10.75 feet. Then multiply 12.5 × 10.75 = 134.375 square feet, usually rounded to 134.38 sq ft.
Square feet formulas by shape
Use the formula that matches the shape you are measuring. For complex rooms, combine several simple shapes.
| Shape | Formula | When to use it |
|---|---|---|
| Rectangle / square | length × width | Rooms, houses, walls, patios, rugs and most simple lots |
| Triangle | (base × height) ÷ 2 | Angled corners, triangular garden beds and roof sections |
| Circle | π × radius × radius | Round rugs, circular patios, tables and firepit areas |
| Irregular room | Area 1 + Area 2 + Area 3 | L-shaped rooms, alcoves, open-plan sections and whole homes |
Room examples: how to figure square footage
These examples cover the most common square-footage situations: rooms, walls, patios, triangular spaces and L-shaped layouts.
Bedroom
A bedroom that is 11 feet by 13 feet has 143 square feet. Multiply 11 × 13.
Living room
A living room that measures 18 feet by 14 feet has 252 square feet. Add alcoves separately.
Wall area for paint
A wall that is 12 feet wide and 8 feet high has 96 square feet of surface area.
Circular patio
A patio with a radius of 6 feet has about 113.10 square feet using π × 6 × 6.
Triangular area
A triangular corner with a base of 10 feet and a height of 8 feet has 40 square feet.
L-shaped room
Split into two rectangles: 12 × 10 and 8 × 7. Total = 120 + 56 = 176 square feet.
How to calculate square footage for a house or apartment
For a home or apartment, calculate each room or section separately, then add all the results. For example:
- Living room: 16 × 12 = 192 sq ft
- Bedroom: 12 × 11 = 132 sq ft
- Kitchen: 10 × 9 = 90 sq ft
- Bathroom: 8 × 5 = 40 sq ft
The combined total is 454 square feet. If you are estimating materials, decide whether closets, built-ins, cabinets or other fixed areas should be included.
How to calculate square feet for flooring, tile, carpet, or laminate
For flooring, calculate the raw area first, then add extra material for cuts, waste, pattern matching or breakage. A common guideline is 5% extra for straightforward installations and 10% to 15% extra for tile, patterned flooring, angled cuts or beginner DIY projects.
If your room is 200 sq ft and you add 10% waste, plan for about 220 sq ft of material. The calculator above includes a waste percentage so you can see the buying number, not just the raw area.
How to calculate square footage for walls and paint
For walls, use width × height. A wall that is 14 feet wide and 8 feet high has 112 square feet. For paint estimates, subtract large doors or windows if you want a tighter coverage number. For a fast estimate, many people calculate the full wall area first and adjust later.
How to calculate square feet for land, yards, and outdoor spaces
Outdoor spaces use the same area rules. A rectangular patio is length × width. A triangular garden bed is base × height ÷ 2. A circular firepit zone is π × radius². For irregular land or yards, split the space into simple shapes where possible.
For land conversions, use the acre to square feet converter or broader area converter.
Square feet conversions you will use most often
These are the conversions most likely to matter for room plans, construction drawings, flooring, land and metric measurements.
| From | To square feet | Notes |
|---|---|---|
| 1 square foot | 1 sq ft | The base unit used on this page. |
| 1 square meter | 10.7639 sq ft | Useful when plans are metric. |
| 1 square yard | 9 sq ft | Common in carpet and fabric contexts. |
| 1 acre | 43,560 sq ft | Common for land and lot size. |
| 1 sq ft | 144 square inches | Helpful when inch-based measurements are available. |
Worked examples for common room sizes
Use these examples to check whether your calculation looks reasonable.
| Room size | Calculation | Total square feet |
|---|---|---|
| 10 × 10 | 10 × 10 | 100 sq ft |
| 10 × 12 | 10 × 12 | 120 sq ft |
| 12 × 12 | 12 × 12 | 144 sq ft |
| 12 × 15 | 12 × 15 | 180 sq ft |
| 14 × 16 | 14 × 16 | 224 sq ft |
| 15 × 20 | 15 × 20 | 300 sq ft |
| 20 × 20 | 20 × 20 | 400 sq ft |
How to measure an irregular or L-shaped room
Break the layout into rectangles. For an L-shaped room, draw an imaginary line that splits the room into two boxes. Measure each box separately, calculate each area, then add them together.
- Main section: 14 × 10 = 140 sq ft
- Smaller section: 8 × 6 = 48 sq ft
- Total: 140 + 48 = 188 sq ft
How to calculate square footage when each side is different
If opposite sides are not equal, the shape is probably not a rectangle. For a practical estimate, split the space into rectangles and triangles. For accurate buying or installation decisions, avoid using a rough average unless the estimate is acceptable.
Mistakes that cause wrong square-foot calculations
The calculation is simple, but the same avoidable errors appear often.
Using feet and inches as decimals
12 feet 6 inches is 12.5 feet, not 12.6 feet.
Mixing units
Do not multiply one dimension in feet and another in inches or meters.
Forgetting extra material
Raw area is not always the purchase quantity. Flooring and tile often need extra.
Not splitting irregular spaces
An L-shaped room should be split into separate rectangles before adding totals.
Confusing area with perimeter
Perimeter is the distance around the edge. Square feet measures surface area.
Over-rounding too early
Keep precise measurements until the end, especially for larger projects.
Square feet vs cubic feet
Square feet measures flat area. Cubic feet measures volume and includes depth or height. Use square feet for coverage, such as floors, walls, patios and yards. Use cubic feet when you are filling space, such as soil, concrete, gravel or storage volume.
When to subtract doors, windows, closets, or cabinets
It depends on the purpose. For paint, subtracting large windows and doors can improve accuracy. For flooring, built-ins may or may not be included depending on the installation. Decide whether you need gross area or usable coverage area before finalizing the number.
How to estimate material from square feet
Once you know the area, compare it with the coverage or box size of the material you are buying. For flooring, tile, carpet, turf and many sheet materials, add waste. For paint, compare wall square footage with the coverage per can. For gravel, concrete or soil, add depth and calculate volume.
Useful follow-up tools include the meters to feet converter, length conversion calculator, inch to centimeter calculator, and acre to square feet converter.
Why the formula is easy to remember
If one foot by one foot makes one square foot, then a 10 ft by 12 ft room contains 120 one-foot squares. Length × width is a compact way of counting those one-by-one squares across a surface.
Related RevisionTown tools and guides
If you are working through measurements, land units or area conversions, these related resources are the most useful next steps.
Area Converter
Convert between square feet, square meters, acres, square yards and other area units.
Acre to Square Feet Converter
Useful for land, lot size, landscaping and outdoor planning calculations.
Meters to Feet Converter
Use this when plans are metric but your buying or listing math is in feet.
Length Conversion Calculator
Convert feet, inches, yards, meters and more before calculating area.
Inch to Centimeter Calculator
Helpful when measuring in imperial units but comparing metric dimensions.
Area and Perimeter Guide
A broader geometry refresher for area, perimeter and measurement skills.
Square feet FAQs
How do you calculate square feet?
For a rectangle or square, multiply length by width using feet for both measurements. If the room is irregular, split it into smaller shapes, calculate each part, then add the totals.
How do you calculate square footage with feet and inches?
Convert each measurement to decimal feet first. Divide the inches by 12 and add that value to the whole feet. Then multiply length by width.
Is square footage the same as square feet?
In everyday usage, yes. Square feet is the unit, while square footage is the total area measured in that unit.
How do I calculate square feet for an L-shaped room?
Split the room into two or more rectangles, calculate each section separately, and add the results.
Do I add rooms together to get total house square footage?
Yes. Measure each room or section separately, calculate its square feet, then add all the room totals for the combined area.
How much extra flooring should I buy?
A common guideline is 5% extra for simple installs and 10% to 15% for tile, complex layouts, or angled cuts.
How do I convert square feet to square meters?
Divide square feet by 10.7639 to get square meters. To convert square meters to square feet, multiply by 10.7639.
What is one square foot?
One square foot is the area of a square that is 1 foot long and 1 foot wide. It is equal to 144 square inches.
Final takeaway
For a rectangular space, use square feet = length × width. For anything more complex, split the area into smaller shapes, calculate each piece, and add them together. For flooring or tile, add extra material so the buying quantity is realistic.