Square Footage Calculator
- Updated Jul 2026
This free square footage calculator finds the area of any room, wall, or plot in seconds. Square footage = length (ft) × width (ft). Enter your measurements in feet, inches, or meters, mixed units are fine — and get results in square feet, square yards, square meters and acres, plus material cost.
Table of Contents
Square Footage Calculator Tool
Enter Your Details
Fill in the fields, then press Calculate.
Fill in your information on the left to see your result.
Results are estimates for planning purposes. Verify quantities for structural or safety-critical work.
How to use this square footage calculator
- Pick your shape — rectangle, square, L-shape, circle, triangle, trapezoid, or a bordered version of any of them.
- Enter the dimensions. The square footage calculator accepts feet and inches together, so 12 ft 6 in needs no conversion by hand.
- Add a waste allowance if you’re ordering material — 10% covers most projects.
- Enter a price per unit for an instant material cost.
Results appear in square feet (ft²), square inches, square yards, square metres and acres at the same time, so you can order in whichever unit your supplier quotes.
How to calculate square footage
Square footage is simply area measured in feet. The core formula is the one most people already know:
Square feet = Length (ft) × Width (ft)
The word “square” just signals that you are measuring a flat, two-dimensional surface rather than a line or a volume. Measure in meters instead and you get square meters; measure in yards and you get square yards. The method never changes, only the unit does.
Step by step
- Measure the length of the space in feet, wall to wall.
- Measure the width the same way.
- Multiply the two figures. A room 16 ft long and 12 ft wide gives 16 × 12 = 192 square feet.
- Add a waste allowance if you’re buying material, then round up to whole boxes or rolls.
That’s the entire method the square footage calculator runs, just without the arithmetic.
Using feet and inches in the square footage calculator
Real rooms are almost never a whole number of feet, and this is where most hand calculations go wrong. You cannot multiply 12 ft 6 in by 10 ft 3 in directly — the inches must become decimal feet first.
Decimal feet = Feet + (Inches ÷ 12)
So 12 ft 6 in becomes 12 + (6 ÷ 12) = 12.5 ft. Then multiply as normal. The square footage calculator does this conversion automatically when you enter both fields, which is why entering feet and inches separately is safer than converting in your head.
| Inches | Decimal feet | Inches | Decimal feet |
|---|---|---|---|
| 1 in | 0.0833 ft | 7 in | 0.5833 ft |
| 2 in | 0.1667 ft | 8 in | 0.6667 ft |
| 3 in | 0.25 ft | 9 in | 0.75 ft |
| 4 in | 0.3333 ft | 10 in | 0.8333 ft |
| 5 in | 0.4167 ft | 11 in | 0.9167 ft |
| 6 in | 0.5 ft | 12 in | 1 ft |
How many inches are in a square foot?
There are 144 square inches in one square foot, not 12. This trips people up constantly. A foot is 12 inches long, but a square foot is 12 in × 12 in, and 12 × 12 = 144.
That gives you two ways to work from inch measurements. Convert each dimension to decimal feet first, or multiply the inches together and divide the result by 144. Both land on the same answer.
Square feet = (Length in inches × Width in inches) ÷ 144
A countertop measuring 96 in × 25 in is (96 × 25) ÷ 144 = 16.67 square feet. For converting individual measurements between inches, feet, centimetres and meters before you start, our length converter handles every combination.
Watch the unit mix. Never multiply feet by inches directly. A room entered as 12 × 150 (feet × inches) returns 1,800 — a figure that is meaningless and roughly 12 times too large.
Area formulas for every shape
Not every space is a rectangle. The square footage calculator covers each of these shapes, and the formulas below let you check the working by hand.
| Shape | Area formula (ft²) | Typical use |
|---|---|---|
| Square | Side × Side | Patios, tiled sections |
| Rectangle | Length × Width | Rooms, floors, plots |
| Rectangle border | Total area − Inner area | Walkways, edging, decking trim |
| Circle | 3.14159 × (Diameter ÷ 2)² | Patios, pools, planting circles |
| Circle border (annulus) | Outer area − Inner area | Rings around pools or trees |
| Triangle | ½ × Base × Height | Corner sections, gable ends |
| Trapezoid | [(a + b) ÷ 2] × Height | Tapered rooms, angled plots |
| Cathedral wall | ½ × Width × (Height 1 + Height 2) | Walls under a sloped ceiling |
For a circle, measure the diameter rather than the radius and if you only have the radius, double it first. Use 3.14159 rather than 3.14 on anything larger than a small patio; the difference compounds quickly across big areas.
How to calculate the square footage of an L-shaped room
Irregular rooms are the most common real-world case, and the fix is simple: divide and conquer. Sketch the floor plan, split it into rectangles, then add the areas together.
Measure section A at 14 ft × 10 ft for 140 square feet, then section B at 6 ft × 5 ft for 30 square feet. Added together, the room is 170 square feet. Run each section through the square footage calculator separately and total the results, the same approach works for U-shapes, bay windows and any bump-out.
How to calculate the square footage of a wall
- Measure the wall height from floor to ceiling, excluding baseboards and mouldings.
- Measure the wall length, including any doors and windows for now.
- Multiply height × length for the gross wall area.
- Measure each window and door, and subtract those areas for the true paintable surface.
A wall 20 ft long and 8 ft high is 160 square feet gross. Take out a 3 ft × 5 ft window (15 ft²) and a 3 ft × 7 ft door (21 ft²) and you are left with 124 square feet to cover. Once you have that number, our paint calculator converts it into the exact number of gallons or litres for your chosen number of coats.
Multiple identical windows? Multiply one window’s width by the number of windows and enter that as a single width. The height stays the height of one window.
How to calculate the square footage of a house
Whole-house measurement follows different rules from a single room, because not every space counts. If the house is a simple rectangle, measure the outside length and width per floor and add the floors together. Most houses aren’t that simple, so work room by room:
- Sketch a rough floor plan of each level.
- Measure each room wall to wall and calculate its area.
- Note each figure on the plan.
- Add every room together for total finished living area.
| Usually counts as living area | Usually excluded |
|---|---|
| Bedrooms, living and dining rooms | Garages, attached or not |
| Kitchens and bathrooms | Unfinished basements |
| Hallways, staircases, closets | Unheated porches and patios |
| Finished, heated basements (often listed separately) | Attics under 5 ft of headroom |
Rules vary by region and lender, and appraisers in the US typically follow the ANSI Z765 measurement standard. For a listing, mortgage or tax filing, treat the square footage calculator as a working estimate and have an appraiser confirm the official figure.
Can you convert feet to square feet?
Not directly, and this is one of the most common misunderstandings about area. Feet measure length in one dimension; square feet measure surface across two. A single measurement of “10 feet” describes a line, not a space, so there is no conversion factor between them.
What you can do is supply the missing dimension. If a hallway is 10 feet long and 4 feet wide, it covers 40 square feet. Ask “10 feet is how many square feet?” and the honest answer is that it depends entirely on the width. The same logic applies to linear feet of timber or trim: you need a width before
Adding a waste allowance to your square footage
The square footage calculator gives you the exact area, but you should never order exactly that much material. Offcuts, pattern matching, breakages and awkward corners all consume stock. Ordering roughly 10% extra is standard practice.
| Material | Suggested surplus | Why |
|---|---|---|
| Vinyl / laminate, simple room | 5–10% | Straight runs, few cuts |
| Vinyl / laminate, complex room | 10–15% | Angles, doorways, alcoves |
| Carpet | 10% | Pattern matching and seams |
| Ceramic and porcelain tile | 10–15% | Cuts and breakages |
| Hardwood flooring | 10% | Board grading and offcuts |
| Paint | 10% | Touch-ups and absorption |
| Diagonal or herringbone layouts | 15–20% | Far more angled cuts |
Applying it is straightforward: 170 square feet × 1.1 = 187 square feet to order. To work out any other percentage uplift quickly, our percentage calculator does it in one step.
Working out cost per square foot
Suppliers quote in different units, so check before comparing. Carpet is often priced per square yard, imported tile per square metre, and flooring per box covering a fixed area. Divide the box price by its coverage to get a true price per square foot, then compare like with like.
At $3.50 per square foot, a 187 square foot order costs $654.50. Enter the rate into the square footage calculator and it returns the total alongside the area.
Converting square feet to other units
The square footage calculator reports every unit at once, but these are the factors if you’re checking by hand:
At $3.50 per square foot, a 187 square foot order costs $654.50. Enter the rate into the square footage calculator and it returns the total alongside the area.
| Convert from | To | Operation |
|---|---|---|
| Square inches | Square feet | Divide by 144 |
| Square feet | Square yards | Divide by 9 |
| Square feet | Square metres | Multiply by 0.0929 |
| Square metres | Square feet | Multiply by 10.7639 |
| Square feet | Acres | Divide by 43,560 |
| Acres | Square feet | Multiply by 43,560 |
Land and plot sizes are usually quoted in acres, and our acres to square feet converter handles that conversion on its own if it’s all you need.
Common square footage mistakes
- Multiplying feet by inches. Convert everything to one unit first, or use the separate feet and inches fields.
- Assuming 12 square inches per square foot. It’s 144.
- Measuring only the widest points of an irregular room, which overstates the area — split it into rectangles instead.
- Forgetting to subtract openings when calculating walls for paint or wallpaper.
- Ordering the exact area with no waste allowance.
- Confusing area with volume. Mulch, soil, gravel and concrete are sold by volume, so you’ll need depth as well as area.
For those bulk materials, take your area figure and continue with our cubic yard calculator, which turns square footage plus a depth into orderable cubic yards.
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Work out tons and cubic yards of gravel for driveways, paths, patios and drainage beds.
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Frequently asked questions
How do you calculate square footage?
Multiply length in feet by width in feet. A room 16 ft by 12 ft is 192 square feet. For other shapes, use the matching area formula.
How many inches are in a square foot?
144. A square foot is 12 inches by 12 inches, and 12 × 12 = 144 square inches.
How do I convert feet and inches to square feet?
Turn the inches into decimal feet by dividing by 12, then multiply. 12 ft 6 in becomes 12.5 ft. Alternatively, multiply both dimensions in inches and divide by 144.
Can you convert linear feet to square feet?
Not without a second measurement. Linear feet describe length only, so you need the width before you can calculate area.
How do I measure an L-shaped or irregular room?
Split it into rectangles, calculate each one separately, then add the areas together.
How much extra material should I order?
About 10% for most projects, rising to 15–20% for tile, complex layouts or diagonal patterns.
What counts towards a house's square footage?
Finished, heated living space including hallways, staircases and closets. Garages, unfinished basements and unheated porches are normally excluded.
How big is 1,000 square feet?
Roughly a 32 ft by 32 ft square, or about the size of a two-bedroom apartment. Any pair of dimensions multiplying to 1,000 gives the same area.
**References and further reading
- American National Standards Institute (ANSI) Z765 — the standard method for measuring single-family residential square footage in the US.
- American Society of Home Inspectors and appraisal bodies — guidance on what counts as finished living area.
- Manufacturer installation guidelines — recommended waste allowances vary by flooring type and layout.