Square Footage Calculator - Rooms, Odd Shapes & Cost

How to use it

1. Sketch the floor on paper first and put a name on every room. The list in the tool should match the list in your hand.
2. Measure each room at floor level along the baseboard, to the nearest inch, and measure both ends of every wall.
3. Type feet and inches in their own boxes. 12 ft 7 in goes in as 12 and 7, never as 12.7.
4. Pick the shape. A room with a bite out of it is an L-shape: give the outer rectangle, then the notch.
5. Add deductions for anything the material will not cover, like a kitchen island, a stairwell opening or a hearth.
6. Add a room for every extra space, or set a quantity when several rooms are genuinely identical.
7. Read the total, check the drawn plan against your sketch, then read the hand-off lines to see what to actually order.
8. Switch to Walls mode for paint, drywall or wallpaper, House mode for a listing figure, or Convert for units and the room size chart.

At a glance

• A 12 ft by 10 ft bedroom: 120.0 sq ft. Order about 132 sq ft of flooring at 10 percent waste, or 13.3 sq yd if the quote comes in yards.
• A three-room main floor: Living room 222.2, an L-shaped kitchen 161.0, hallway 42.0. Total 425.2 sq ft, and the flooring line says order about 468 sq ft.
• 12 ft 7 in by 10 ft 4 in, typed properly: 130.0 sq ft. Typed as 12.7 by 10.4 the same room reads 132.1, and that two square foot error repeats in every room on the floor.
• A 12 by 14 bedroom, walls only: 416 sq ft of wall before openings, 366 after one door and two windows. That is 12 sheets of drywall or 2.1 gallons of paint at two coats.
• A 28 by 40 two-story house: 2,240 sq ft finished. Add the garage and the covered porch and the tape says 2,820. Both are honest; they answer different questions.

How the math works

Everything is held in inches and converted at the end, which is the whole reason feet and inches get their own boxes. A room is length in inches times width in inches, an L-shape is the outer rectangle minus the notch, a circle is pi times the diameter squared over four, a triangle is base times height over two, and a trapezoid is the average of the two parallel sides times the height. Deductions come off before the quantity multiplies, so three identical bedrooms with a closet each deduct three closets. The sum of the rooms in square inches divides by 144 to give square feet. The per-room column you read is apportioned against that total, which means the rows on the takeoff table always add up to the headline exactly, even when rounding would otherwise leave a tenth adrift. Below 1,000 sq ft everything prints to one decimal; above it, to whole square feet, because a tenth of a square foot on a 2,000 sq ft house is noise pretending to be precision.

1. Measure at the floor, not at the ceiling line

   Run the tape along the baseboard. Crown moulding, a soffit over the cabinets and a sloped ceiling all lie about the floor underneath them, and the floor is what you are buying material for. If the baseboard is already off, measure wall to wall at the subfloor and note it, because a quarter inch of drywall on each side is half an inch of room you will get back.

2. Measure both ends of every wall and keep the larger figure

   Rooms are rarely square. A 12 ft wall that reads 12 ft 1 in at the far end is normal, and the difference matters when a plank run has to reach. Take both ends, keep the larger, and you will never be short. If the two ends differ by more than about an inch, the room is out of square enough that you should split it as a trapezoid rather than average it.

3. Split anything odd into shapes you can measure honestly

   A room with a bay window, a chimney breast or a pantry cut into the corner is not one rectangle. Draw the biggest rectangle you can, then treat what is left as its own room or as a notch. An L-shaped kitchen at 14 ft by 12 ft 6 in with a 4 ft by 3 ft 6 in pantry notch is 175 sq ft minus 14 sq ft, which is exactly the same as a 10 ft by 12 ft 6 in slab plus a 4 ft by 9 ft leg. Both routes give 161 sq ft, so use whichever one matches how you measured it.

4. Enter feet and inches as feet and inches

   12 ft 7 in is 12.583 ft, not 12.7 ft. The tool gives inches their own box so the conversion never has to happen in your head. Inches over 12 are accepted and carry, so 11 ft 24 in reads as 13 ft, and a comma decimal works as well as a period for anyone on a European keyboard layout.

5. Decide what to deduct, then deduct it once

   A kitchen island on a tiled floor is a real deduction because the tile stops at its base. The same island on a floating floor usually is not, because the floor runs under it. A stairwell opening always comes out. Deduct on this page or in the material calculator, but never in both, or you will end up ordering a floor that is 30 sq ft short.

6. Translate the area, do not just report it

   The number on the tape is not the number on the order. Flooring wants area plus a waste allowance, tile wants more of one at 45 degrees, carpet wants a roll layout rather than an area, concrete wants area times a depth in cubic yards, sod wants pallets, and paint wants a completely different measurement. The hand-off lines under the total do that translation and then send you to the page that does it properly.

Worked scenarios, start to finish

Real jobs with the numbers carried all the way through, so you can see how the estimate is built and check your own figures against them.

The judgement calls a pro makes

Decisions the tool cannot make for you, and how someone who does this for a living thinks them through.

Closets: in for flooring, usually out for furniture

If the floor runs into the closet, its area is material you have to buy, so add it as its own small room. If you are working out whether a sofa fits or how much heat the room needs, closets are dead space and leaving them out gives you a truer picture. The same room can honestly have two different square footages depending on the question.

Under the appliances and under the cabinets

Flooring almost always runs under a dishwasher and a range, because they have to be able to slide out, so count that area. It usually stops at the toe kick of a fixed cabinet run, so a full-height galley of base cabinets is a genuine deduction on a tile job. On a floating floor, run it wall to wall and deduct nothing, because the expansion gap needs a continuous field.

Bay windows, alcoves and anything under 3 ft deep

A bay window with a floor at the same level as the room is floor you are buying material for, so measure it as a small trapezoid or rectangle and add it. A window seat with a raised platform is not. The rule of thumb is simple: if you could stand on it in socks and it is the same surface, it counts.

Deducting a kitchen island

Deduct it for tile, stone or anything set in mortar, because those genuinely stop at the base. Do not deduct it for a floating floor or for carpet, where the material runs underneath or the offcut would be worthless anyway. When in doubt, leave it in: a 20 sq ft over-order is a spare box, and a 20 sq ft shortfall is a second trip and a dye lot mismatch.

Round up per room, or once at the end

If you are ordering one material for the whole floor, add the rooms first and round once, which is what this page does. If each room gets a different material, round each room up on its own, because you cannot spread one spare box across three products. The difference on a five-room floor is usually a box either way.

What to do about a room that is badly out of square

If the two ends of a wall differ by more than an inch or so, do not average them. Enter the room as a trapezoid with the two parallel sides and the depth between them, which is exact rather than approximately right, and the drawn plan will show you the taper so you can sanity check it against the room.

Common mistakes, and the fix

• × Typing 12 ft 7 in as 12.7. It looks right and it is wrong by nearly an inch and a half.

  ✓ 12 ft 7 in is 12.583 ft, so a 12 ft 7 in by 10 ft 4 in room is 130.0 sq ft, not 132.1. That is 2.1 sq ft of phantom floor per room, and across a five room floor it is most of a box of flooring bought for nothing. Feet and inches have their own boxes here so the conversion never happens in your head.

• × Measuring one wall and assuming the wall opposite matches.

  ✓ Measure both ends of every run. Houses settle and framing wanders, so a 1 in difference over 14 ft is completely normal. Keep the larger figure and you will never come up short on a plank run.

• × Buying paint or drywall off the floor area.

  ✓ Floors and walls are different measurements and they are rarely close. A 12 by 14 bedroom has 168 sq ft of floor and 366 sq ft of paintable wall. Switch to Walls mode, which figures perimeter times ceiling height and takes the doors and windows out.

• × Adding a waste allowance here and then adding it again in the material calculator.

  ✓ Add it once. This page measures and previews; the material pages own the real waste rules, because 10 percent for a straight lay and 15 percent for a herringbone are not interchangeable. Every preview line here says which figure it has already adjusted.

• × Counting a stairwell on both floors in house mode.

  ✓ The stair counts once on each floor it actually serves as floor area, and the open hole above it is not floor at all. Measure the second-floor footprint with the stairwell opening deducted, or you will sell 40 sq ft of air.

• × Mixing square yards and square feet when a carpet quote comes back.

  ✓ Carpet is still quoted by the square yard in much of the trade, and one square yard is nine square feet, not three. A 425 sq ft floor is 47.2 sq yd. The conversions strip prints both so a quote can be checked in the units it arrived in.

• × Trusting a listing square footage you did not measure.

  ✓ Listing figures follow a convention rather than a tape, and they can be years old. Measure the rooms you are actually buying material for. If the two numbers disagree by more than a couple of percent, the tape wins.

Material and unit specifics

Which number each material wants

Flooring, tile, carpet, vinyl and laminate take floor area. Paint, drywall, wallpaper and panelling take wall area, which is perimeter times ceiling height minus openings. Concrete, gravel, mulch, topsoil, sand and asphalt take area times a depth, so they come out in cubic yards rather than square feet. Sod takes lawn area and is sold by the pallet. Getting the family right matters more than getting the decimal right.

Waste norms by material

Flooring runs 5 to 10 percent for a straight lay in a simple room, more once you have a diagonal, a stair nose or several doorways. Tile runs 10 percent straight, 15 percent for a diagonal or herringbone, and more for a mosaic sheet that has to be cut to a curve. Sod runs about 5 percent for the cuts around beds. Carpet does not take a percentage at all, because a 12 ft roll either covers your room in one cut or it does not.

Why carpet breaks area math

Broadloom arrives as a roll 12 ft wide, occasionally 13 ft 6 in or 15 ft. A 14 ft wide room needs a 12 ft cut plus a 2 ft fill strip and a seam, so you buy 14 ft of roll length regardless of what the area says. That is why the carpet line on this page gives you square yards and then tells you to go and do the roll layout properly.

Square inches, square yards, square metres, acres

To convert square inches to square feet, divide by 144. One square yard is 9 square feet. To convert square feet to square metres, multiply by 0.0929. One acre is 43,560 square feet, which is a hair under a 209 ft square. The converter runs all of these both ways.

Cost per square foot, as a planning range

Typical installed ranges, to be checked against local quotes rather than trusted: flooring 3 to 12 dollars a square foot, tile 8 to 25, carpet 2 to 8, concrete slab 6 to 12, sod 1 to 2. On wall area: interior painting 1.50 to 4 dollars a square foot and drywall hung and finished 2 to 3.50. Labour is usually the larger half in every one of those bands, and it swings hardest by region.

Finished square footage, as listings usually count it

The common convention counts finished, heated, above-grade space that you reach without going through an unfinished area. Attached garages, open porches, unfinished basements and attic space under about 5 ft of headroom are excluded, and stairs count on each floor they serve. Below-grade finished space is usually listed separately rather than added in. Markets differ, so this is planning and listing context and never an appraisal.

Measuring a lawn without a map tool

Break the lawn into rectangles against the fence lines, the drive and the beds, and measure each one with a tape or by pacing. A comfortable adult pace is close to 2 ft 6 in, so 20 paces is roughly 50 ft, which is accurate enough for sod within a pallet. Add the rectangles as rooms here, then take the total to the sod page for the pallet order.

Reading your result

The headline is the measured area and nothing else. It is the truth about your space, and it is almost never the number you hand over at a trade counter. The lines under it are the translation: flooring wants the area plus a waste allowance, tile wants more of one once the pattern turns, carpet wants a roll layout, concrete wants a depth, sod wants pallets, and paint wants a completely different measurement altogether. Read the drawn plan as a check rather than as decoration: if a room in the drawing looks nothing like the room you are standing in, a number is wrong somewhere. In house mode the two figures are both real, and the gap between finished and gross is space that belongs in the description rather than the headline. The cost ledger is planning arithmetic on prices you type in yourself, which makes it a sanity check on a quote, never a quote of its own.

Limitations

• No map, satellite or GPS measuring. Everything here comes from a tape you hold, which is why the numbers are as good as your measuring and no better. For a lawn, break it into rectangles against the fence and the beds and add them as rooms.
• Regular geometry only. A genuinely curved wall has to be approximated by splitting it into a few straight sections or a part-circle, and the more sections you use the closer you get.
• Metric entry is not supported in version one. Enter in feet and inches and read square metres off the conversions strip, which is exact.
• House mode presents the common listing convention for finished square footage. It is planning context, not an appraisal, and the rule varies by market, so confirm it with a local agent or appraiser before a listing goes live.
• The cost ranges are typical national bands for planning. Local labour, access, subfloor condition and how much of the old material has to come out will move a real quote well outside them.
• Deductions are rectangles. An irregular obstruction has to be approximated, and for anything smaller than a couple of square feet it is usually better to ignore it and let the waste allowance absorb it.

Frequently asked questions

How many square feet is a 12x12 room?

144 square feet. Multiply 12 ft by 12 ft. The same arithmetic gives 100 sq ft for a 10 by 10, 180 for a 12 by 15, 400 for a 20 by 20 and 1,200 for a 30 by 40. The room size chart on this page lists the common ones, and the converter will do any pair you type in, including the inches.

How do I calculate the square footage of a room?

To find the square footage of a room, multiply the length in feet by the width in feet. For feet and inches, either divide the inches by 12 first (12 ft 7 in is 12.583 ft) or work in inches and divide the result by 144, which is what this tool does internally so nothing is lost to rounding. For a room that is not a rectangle, split it into rectangles, work out each one, and add them together.

What counts in a house's square footage?

Under the convention most listings follow, finished, heated, above-grade space counts, and it has to be reachable without walking through an unfinished area. Stairs count on each floor they serve. Attached garages, open porches, unfinished basements and attic space under roughly 5 ft of headroom do not count, and finished basement space is usually listed separately rather than added in. This is planning and listing context rather than an appraisal, and the rule varies by market.

How many square feet are in an acre?

43,560 square feet. That is a square about 209 ft on a side, or roughly 90 percent of an American football field without the end zones. To go the other way, divide square feet by 43,560. The converter on this page prints acres alongside square inches, square yards and square metres.

How do I convert square inches to square feet?

Divide by 144, because a square foot is 12 in by 12 in. So 288 sq in is 2 sq ft, and 1,000 sq in is 6.94 sq ft. The common mistake is dividing by 12, which is the linear conversion and gives an answer twelve times too big.

How do I convert linear feet to square feet?

You cannot, without a width. Linear feet measure length alone, which is how trim, fencing and countertop edging are sold. Multiply the linear feet by the width in feet to get square feet: 40 linear ft of a 6 in wide board is 40 times 0.5, which is 20 sq ft. If you are buying planks by the linear foot, divide your area by the plank width in feet to get the linear feet you need.

How do I measure square footage for flooring?

Measure each room separately at floor level, name it, and add the rooms up rather than pacing the whole floor as one shape. Include closets if the floor runs into them, deduct anything the floor genuinely stops at, and then add a waste allowance of about 10 percent, which is what the flooring line under the total does for you. Take that adjusted figure, not the raw area, to the flooring calculator for the box count.

Should I add waste here or in the material calculator?

Once, in the material calculator. This page measures and shows you a preview of the adjusted number so you know roughly what you are in for, and each preview line says what it already adjusted. The material pages own the real rules, because the right allowance depends on the pattern, the plank length, the number of doorways and the room shape, none of which a flat percentage on an area knows about.