Add the installed or material price to see the cost of the area with waste included.
See full breakdown
To find square footage, multiply the length by the width in feet: a 12 × 10 ft room is 120 sq ft. For a triangle, multiply the base by the height and divide by 2; for a circle, multiply π (3.1416) by the radius squared. Odd shaped spaces are split into simple shapes and the pieces added together. Divide square feet by 9 to get square yards, or multiply by 0.0929 for square meters, and order about 10% extra material to cover cuts and waste.
How to calculate square footage
How this square footage calculator works: each area gets the formula for its shape, every measurement is turned into feet first, and the pieces are added into one total. Cut outs come off, then the waste allowance goes on top.
| Shape | What to measure in feet | Formula | Example |
|---|---|---|---|
| Rectangle | Length and width | Length × width | 20 × 15 = 300 sq ft |
| Square | One side | Side × side | 12 × 12 = 144 sq ft |
| Triangle | Base, and height straight up from it | Base × height ÷ 2 | 10 × 8 ÷ 2 = 40 sq ft |
| Circle | Diameter, across the middle | 3.1416 × (diameter ÷ 2)² | 10 ft across = 78.5 sq ft |
| Trapezoid | Both parallel sides and the height between them | (Top + bottom) ÷ 2 × height | (8 + 12) ÷ 2 × 10 = 100 sq ft |
| L shape | Split into two rectangles | (L1 × W1) + (L2 × W2) | 16 × 12 + 8 × 6 = 240 sq ft |
| Cut out | Anything that will not be covered | Subtract length × width | 144 minus a 4 × 2 hearth = 136 sq ft |
| Total | Every area on the job | Sum of the areas × (1 + waste %) | 444 sq ft + 10% = 488.4 sq ft |
Worked example: a 20 × 15 ft living room and a 12 × 12 ft bedroom, with 10% waste
When to use this square footage calculator
Reach for it on any project that needs an accurate area or a cost worked out from one, inside or out.
- Flooring installation: tile, carpet, laminate or hardwood. Measure each room as its own area, cut out the kitchen island or the hearth, and the Materials tab turns the total into boxes of plank or square yards of carpet with the right waste for that floor.
- Painting projects: wall or ceiling coverage turned into gallons of paint.
- Landscaping: sod for a lawn, mulch or gravel for beds, pavers for a patio. Curved beds work as circles or as a known area, and the result comes out in pallets or cubic yards, which is how a yard or nursery sells it.
- Interior design: check rug sizes and how much floor a furniture layout really leaves.
- Construction planning: drywall, insulation and roofing materials all start from an area. Walls are length × height with doors and windows cut out; for a pitched roof, the roofing calculator adds the slope.
- Real estate: verify a home's size for a listing or an appraisal, keeping in mind that garages and basements sit outside the living area figure.
- Contractor quotes: a square feet calculator with a price field gives a per square foot quote in one step.
How many square feet is a room?
Length times width, worked out for the sizes people look up most. A 12 × 12 room is 144 sq ft and a 30 × 40 space is 1,200 sq ft.
| Size (ft) | Square feet | Square yards | Square meters |
|---|---|---|---|
| 2 × 2 | 4 | 0.4 | 0.4 |
| 10 × 10 | 100 | 11.1 | 9.3 |
| 10 × 12 | 120 | 13.3 | 11.1 |
| 12 × 12 | 144 | 16 | 13.4 |
| 12 × 15 | 180 | 20 | 16.7 |
| 15 × 20 | 300 | 33.3 | 27.9 |
| 20 × 20 | 400 | 44.4 | 37.2 |
| 24 × 24 | 576 | 64 | 53.5 |
| 30 × 40 | 1,200 | 133.3 | 111.5 |
| 40 × 60 | 2,400 | 266.7 | 223 |
Swap the numbers around and the answer stays the same: 15 × 12 is still 180 sq ft.
How do you convert square feet to square yards, meters and acres?
Carpet is priced by the square yard, imported tile by the square meter and land by the acre. One multiplication gets you from one to the other, and this square feet calculator shows all four at once.
| To turn | Into | Do this |
|---|---|---|
| Square feet | Square yards | Divide by 9 |
| Square yards | Square feet | Multiply by 9 |
| Square feet | Square meters | Multiply by 0.0929 |
| Square meters | Square feet | Multiply by 10.764 |
| Square inches | Square feet | Divide by 144 |
| Square feet | Acres | Divide by 43,560 |
How much area does a gallon, box, pallet or yard cover?
Once you know the square footage, these averages turn it into an order. The coverage printed on the can, carton or delivery ticket always wins over an average.
| Material | One unit covers | Good to know |
|---|---|---|
| Paint, 1 gallon | 350 to 400 sq ft | A quart covers about 100 sq ft. Measure walls as length × height. |
| Primer, 1 gallon | 200 to 300 sq ft | Count it as its own line, apart from the topcoat. |
| Laminate flooring, 1 box | 20 to 25 sq ft is most common | Cartons run anywhere from 18 to 32 sq ft, so read the label before you divide. |
| Carpet | Sold by the square yard (9 sq ft) | Rolls come 12 or 15 ft wide, so the room's width decides where the seams fall. |
| Concrete, 1 cubic yard | 81 sq ft at 4 in thick | 65 sq ft at 5 in, 54 at 6 in, 41 at 8 in. |
| Mulch or gravel, 1 cubic yard | 324 sq ft at 1 in deep | 162 sq ft at 2 in and 108 at 3 in, the depth most landscapers spread mulch. |
| Sod, 1 pallet | About 450 sq ft | Pallets come in 400, 450 or 500 sq ft loads and some reach 700. Each piece is about 16 × 24 in. |
| Drywall, 1 sheet | 32 sq ft (4 × 8) | A 4 × 12 sheet covers 48 sq ft with fewer seams. |
Concrete, mulch and gravel are ordered by volume: area × depth in feet ÷ 27 gives cubic yards.
How much extra material should you order?
For most jobs, order about 10% more than the measured area. Diagonal tile, patterned carpet and rooms full of corners need more.
| Material | Extra to order |
|---|---|
| Laminate or vinyl, simple room | 5% to 10% |
| Laminate or vinyl, complex room | 10% to 15% |
| Ceramic tile | 10% to 15% |
| Hardwood flooring | 10% |
| Carpet | 10%, up to 15% for patterns |
| Paint | 10% |
| Drywall, simple room | 5% to 10% |
| Drywall, angles and arches | 15% to 20% |
| Concrete | A little left over: about 1 yard on a 20 yard pour |
Picking a material in the Materials tab fills in its usual waste. Change it if your layout is simpler or harder than average.
What counts toward the square footage of a house?
Listings and appraisals use the ANSI Z765 measuring standard, which Fannie Mae has required for appraisals since April 2022. Only finished space above ground level counts as living area.
| Space | Counted in living area? |
|---|---|
| Finished rooms above grade | Yes, when the ceiling is at least 7 ft high. |
| Rooms with a sloped ceiling | Only if at least half the room reaches 7 ft. Any part under 5 ft is left out. |
| Basements | No. A level counts as below grade if any part of it is below ground, however nicely it is finished, so it is reported on its own line. |
| Garages | No. |
| Staircases | Yes, on the floor the stairs go down from. |
| Two story foyers and other open space | Not on the upper floor. The opening to the floor below is not counted twice. |
Appraisers measure to the nearest inch or tenth of a foot and report the total to the nearest whole square foot.
How do contractors measure a job for a quote?
Flooring, paint, drywall and landscaping crews all price from the same thing, a clean area. This is how to get it right the first time, so the quote and the order both hold up.
- Sketch the spaceDraw the plan on paper or a tablet and split it into rectangles, triangles and circles before the tape comes out.
- Measure each pieceWall to wall at floor level, to the nearest inch. Write each number on the sketch as you go, because a figure you remember in the truck is a figure you guessed.
- Take out what stays bareIslands, hearths, built ins, and doors and windows on a wall.
- Add waste for the materialUse the allowance for that product and that layout. A diagonal tile pattern or a room with six corners needs more than a plain box.
- Round up to whole unitsBoxes, gallons, pallets and yards are sold whole.
- Price per square footMultiply the area by your installed price and put the area on the quote as its own line. A customer who can see the square footage argues less about the total.
The Materials to buy tab runs steps 4 and 5 for you, and the print button gives you the breakdown to attach.
You can't hold a tape measure and answer the phone at once.
Flooring, painting and landscaping crews spend the day measuring rooms and yards, and the calls that come in meanwhile roll to voicemail. ServiceAgent picks up every one of them, asks the caller what needs measuring and how big it is, puts the site visit on your schedule and texts you the details before you are back in the truck.
Book a free demoFrequently asked questions
Quick answers on measuring areas, converting units and using this calculator on real jobs.
Book a free demoHow do I calculate square footage?
Measure the length and the width in feet and multiply them. A room 14 ft long and 11 ft wide is 154 sq ft. If you measured in inches, divide the result by 144; if you measured in meters, multiply by 10.764. For a room with more than one section, work out each section and add them together.
How many square feet is a 12x12 room?
A 12 × 12 ft room is 144 sq ft, which is 16 square yards or about 13.4 square meters. Flooring for it should be ordered with waste on top, so plan on roughly 158 sq ft at 10% extra.
How many square feet is 30x40?
30 × 40 ft is 1,200 sq ft, the same as 133.3 square yards or about 111.5 square meters. Poured as a 4 inch slab, that area takes a little under 15 cubic yards of concrete before any extra.
What size is 4 square feet?
4 sq ft is a 2 × 2 ft square, or any shape whose length times width comes to 4, such as 1 × 4 ft. In square inches that is 576, since every square foot holds 144.
What units does this square feet calculator use?
You can enter measurements in feet, inches, yards, meters or centimeters, and feet and inches together (type 12 6 for 12 ft 6 in). Every result is shown in square feet, square yards, square meters and acres, so you can match whatever unit your supplier prices in.
Can I use it for outdoor spaces like patios or lawns?
Yes. Measure the patio, lawn or garden bed the same way, using circles, triangles or a known area for curved or odd edges. The Materials tab then turns the area into pallets of sod, cubic yards of mulch or gravel, or cubic yards of concrete for a slab.
Is this calculator useful for real estate?
Yes, for a quick check of a listing or a floor plan. Appraisals follow stricter rules: only finished, above grade space with ceilings of at least 7 ft counts toward living area, and garages and basements are left out. To compare homes by price per square foot, use the price per square foot calculator.
Can I calculate multiple rooms at once?
Yes. Add one area per room with the Add an area button, pick each room's shape, and the calculator adds them into one total. Each room's own size shows in the breakdown, and you can print the whole list.
Does this include wall height or volume?
The calculator works out flat area, not volume. For volume, multiply the floor area by the ceiling height: a 300 sq ft room with an 8 ft ceiling holds 2,400 cubic feet. To paint walls, enter each wall as a rectangle of its length × its height and add a cut out for each door and window.
Can I use this for irregular shapes like circles or triangles?
Yes. Pick circle, triangle, trapezoid or L shape for each area. For any other shape, split it into those pieces, add each one as its own area, and use a cut out for anything that should come off the total, like a kitchen island or a hearth.
How does this fit into a contractor's workflow?
Measure on site, print or save the breakdown as a PDF, and copy the link into the job notes so the office can build the quote from the same numbers. ServiceAgent handles the step before that: it answers the calls that come in while you are measuring and books the next site visit.
Leads growth and product marketing for ServiceAgent at SaaS Labs, where he has worked in product marketing since 2020. Writes ServiceAgent's coverage of AI call answering, CRM and home services operations.
Published by ServiceAgent, the AI front office for home service teams. Results are only as accurate as the measurements you enter, and material coverage varies by product. Check the label and measure on site before you order or quote.