Square Footage Calculator: Any Shape, Any Room
Enter dimensions in feet, inches, yards, meters, or centimeters. Get instant area in sq ft, sq m, sq yd, and acres with optional waste factor and cost estimate.
Last updated:Prefer a rectangle-only version with less copy? Use the fast SqFt calculator for the quickest room-size lookup. For the theory behind the formulas, see the guides hub — it covers price per sq ft, linear vs square, cubic vs square, and feet-and-inches measurement.
Tip: If you only have the diameter, divide by 2 to get the radius.
L-shape = two rectangles sharing a corner.
Add one row per rectangle and we'll sum them.
How to Use the Square Footage Calculator
- Pick a shape. Use rectangle, square, circle, triangle, trapezoid, L-shape, or irregular room depending on the layout you need to measure.
- Enter dimensions. Where the shape offers a unit dropdown, choose the unit you actually measured in — the tool converts to feet before calculating.
- Read the result instantly. The tool shows square feet first, then square meters, square yards, acres, and square inches.
- Add waste or price if needed. This is useful for flooring, tile, carpet, and renovation budgeting.
Which Unit Dropdown Applies Where — Read This Before You Mix Units
Most calculators say "supports multiple units" and leave it there. This tool's granularity is not uniform across the seven shapes, and guessing wrong produces an area out by a factor of 12 or 144. The exact behavior, checked against the code that runs the widget:
- Rectangle, triangle, trapezoid: each field has its own dropdown, so units can be mixed freely inside one shape.
- Square, circle: a single selector for a single field.
- L-Shape: one dropdown covers all four numbers — you cannot enter rect 1 in feet and rect 2 in inches on the same tab.
- Irregular: one dropdown per row, shared by that row's length and width, while different rows may use different units.
| Shape tab | Unit selectors | Which fields they govern |
|---|---|---|
| Rectangle | 2 | Length and width, independently. |
| Square | 1 | The side. |
| Circle | 1 | The radius. |
| Triangle | 2 | Base and height, independently. |
| Trapezoid | 3 | Side a, side b, and height. |
| L-Shape | 1 | L1, W1, L2, and W2 all read the same unit. |
| Irregular | 1 per row | That row's length and width; each row chooses for itself. |
Two more consequences of the same code path: on the irregular tab a row you left blank (or filled with 0) is skipped rather than flagged — no warning, it simply adds nothing, so re-check your row count against your sketch. And there is no combined feet-and-inches field: a wall you measured as 12 ft 7 in has to be entered as 12.583 ft, or as 151 in with the unit set to inches. See measuring square footage with inches for the conversion table.
Worked Example: Mixing Feet and Inches in One Room
Enter the shape as rectangle, Length = 12 with ft, Width = 120 with in. The tool converts 120 in to 10 ft before multiplying, so the tiles read:
- 120.00 sq ft — the primary line always shows two decimals and uses a thousands separator
- 11.15 sq m (120 × 0.09290304 = 11.1483648)
- 13.33 sq yd (120 ÷ 9)
- 0.0028 acres (120 ÷ 43,560)
- 17280 sq in (120 × 144) — note the conversion tiles drop trailing zeros and separators, so this reads without a comma while the main line would show 17,280.00
Because the waste field starts at 10%, the same screen also shows "With waste factor you need 132.00 sq ft" — that is the number to order against, not 120.
Cost and Boxes Use the Adjusted Area, Not the Raw Area
This is the single most useful thing to know before trusting a materials quote from any calculator, including this one. Price and box count are computed on the waste-adjusted total:
| Inputs (12 ft × 10 ft room) | Area used | Result shown |
|---|---|---|
| 0% waste, price $4.50/sq ft, coverage 24 sq ft per box | 120 sq ft | $540.00 and 5 boxes |
| 10% waste (the default), same price and coverage | 132 sq ft | $594.00 and 6 boxes |
Boxes always round up (you cannot buy 5.5 boxes), and the waste line, cost line, and box line only appear once their input is greater than zero. Copy Result copies only the square-foot figure, so if you need the cost in a message, type it.
Square Footage Formulas for Every Shape
Square footage is an area measurement. If your measurements are not already in feet, the calculator converts them first and then applies the formula for the selected shape.
| Shape | Formula | Example |
|---|---|---|
| Rectangle | Length × Width | 12 ft × 10 ft = 120 sq ft |
| Square | Side × Side | 10 ft × 10 ft = 100 sq ft |
| Circle | π × r² | π × 6² = 113.10 sq ft |
| Triangle | (Base × Height) / 2 | (14 × 9) / 2 = 63 sq ft |
| Trapezoid | ((a + b) / 2) × h | ((8 + 14) / 2) × 6 = 66 sq ft |
| L-Shape | (L1 × W1) + (L2 × W2) | (16 × 8) + (8 × 6) = 176 sq ft |
| Irregular | Sum of rectangles | (12 × 10) + (8 × 6) = 168 sq ft |
The irregular tab takes any number of rows. Three rows with different units — 12 ft × 10 ft, 96 in × 72 in, and 4 yd × 3 yd — add to 120 + 48 + 108 = 276 sq ft. The yard row is 108 rather than 12 because both sides convert: 4 yd = 12 ft and 3 yd = 9 ft.
Why the Waste Factor Matters
Raw square footage is the floor; the order is the floor plus what the job consumes. Cuts at walls, an offcut too small to reuse, a damaged or mismatched batch, and a small reserve for later repairs all push the purchase above the literal area. How far above depends on the product and the layout: a straight-lay plank floor wastes less than a diagonal lay, and a diagonal or herringbone tile layout wastes more than either.
There is no authoritative standard percentage for any of these. Treat the 0 / 5 / 10 / 15 buttons on the calculator as example starting points, not specifications, and confirm the allowance against the manufacturer's installation guide or your installer's quote before you order. How to measure for flooring walks through the decision room by room.
Popular Use Cases
Flooring Calculator
Estimate hardwood, vinyl, or laminate with waste and pricing.
▤Tile Calculator
Estimate tile counts and box quantities for floors and walls.
▩Carpet Calculator
Square yards, 10% waste, and padding cost in one view.
⌂House Square Footage
Add up multiple finished spaces for whole-home totals.
$Cost per Sq Ft
Convert between total price and area-based budget numbers.
⟟Paint Calculator
Gallons needed at 350 sq ft per gallon for one or two coats.
⇄Sq Ft to Sq M
Quick unit conversion for international projects and listings.
+Multi-Room Total
Sum multiple rectangles when the same flooring covers several rooms.
10×1010x10 Room
How many square feet is a 10x10 room? 100 sq ft.
12×1212x12 Room
How much flooring for a 12x12 room? 144 sq ft.
AllAll Room Sizes
60+ common dimensions from 8x8 to 50x100.
Popular Room Size Questions
- How many square feet is a 10x10 room? — 100 sq ft with flooring, paint, and cost breakdown.
- How much flooring do I need for a 12x12 room? — 144 sq ft base, 158.4 sq ft with 10% waste.
- How to calculate square feet for flooring
- How many gallons of paint for a 10x10 room?
Measurement Tips for Accurate Results
- Measure at floor level, not wall level. Walls are often not plumb, and the lowest point of the wall defines usable floor space.
- Run the tape wall to wall. Do not include baseboards in the reading; they sit on top of the finished floor.
- Measure in two directions. If the two lengths disagree by more than about 1 inch, average them — rooms are rarely perfect rectangles.
- Account for closets and alcoves. Use the L-shape or irregular tabs instead of guessing.
- Write values down before typing. Tape measures are easier to read than retyping from memory.
- Keep room area and house area separate. The US standard for residential square footage, ANSI Z765-2021, measures exterior dimensions to the exterior finished surface of the outside walls and excludes garages and unfinished areas — so a number you build room-by-room here is not automatically the figure an appraisal will show. The room page lists the standard's rules with sources.
When to Use Each Shape
| Shape | Best for | Skip when |
|---|---|---|
| Rectangle / Square | Standard bedrooms, offices, square rooms. | Room has an alcove or bump-out. |
| Circle | Round patios, pools, gazebos. | Shape is more oval than round — split into sectors instead. |
| Triangle | Attic knee-wall spaces, triangular flower beds. | Any obtuse angle that the base-height model can't capture. |
| Trapezoid | Rooms that taper from wide to narrow (common in older homes). | The two "parallel" sides aren't actually parallel. |
| L-Shape | Living rooms with one alcove or a closet bump. | More than two rectangular sections exist. |
| Irregular | Any room you can draw as the sum of rectangles. | The boundary has curves or diagonals. |
Common Conversions You'll Need
- 1 sq ft = 144 sq in — multiply sq ft by 144 for tile-spacing math.
- 1 sq ft = 0.09290304 sq m — the factor is exact, because 1 ft = 0.3048 m by definition; the calculator multiplies by 0.09290304 and displays two decimals.
- 1 sq yd = 9 sq ft — divide sq ft by 9 for carpet orders priced per yard.
- 1 acre = 43,560 sq ft — divide sq ft by 43,560 for land area.
- 1 square of roofing = 100 sq ft — divide sq ft by 100 for shingle bundles.
- Metric input: the tool converts meters with 3.280839895 ft per m, which agrees with the exact 1 ÷ 0.3048 to ten significant figures — far below any tape-measure uncertainty, so a metric entry costs you nothing in practice.
Frequently Asked Questions
How do I calculate square footage of a room?
Measure the length and width in feet and multiply them. For a 12 × 10 ft room, that is 12 × 10 = 120 sq ft. For circles, triangles, trapezoids, and L-shapes, switch to the matching shape tab above and the calculator applies the correct formula automatically.
What is the formula for each shape in the calculator?
Rectangle: length × width. Square: side². Circle: π × r². Triangle: (base × height) / 2. Trapezoid: ((a + b) / 2) × height. L-shape: (l1 × w1) + (l2 × w2). Irregular: the sum of every row's length × width.
Can I enter feet in one field and inches in another?
Yes on the tabs that give each field its own unit dropdown — rectangle, triangle, and trapezoid. Enter Length = 12 ft and Width = 120 in and the tool converts 120 in to 10 ft first, returning 120 sq ft, not 14,400. There is no combined feet-and-inches box, so a 12 ft 7 in wall goes in as 12.583 ft (or 151 in).
Does every shape use the same unit selector?
No. Rectangle, triangle, and trapezoid have one dropdown per field (2, 2, and 3 respectively). Square and circle have one. The L-shape has a single dropdown that covers all four numbers, so you cannot mix feet and inches between its two rectangles. The irregular tab has one dropdown per row, applied to both numbers in that row — and rows you leave blank are skipped rather than flagged.
Is the cost estimate based on the raw area or the waste-adjusted area?
The waste-adjusted area. A 12 × 10 ft room at $4.50/sq ft costs $540.00 at 0% waste and $594.00 at the default 10%, because the price multiplies 132 sq ft rather than 120. Box counts behave the same way and round up: 24 sq ft per box yields 5 boxes at 0% and 6 boxes at 10%.
Why do I need a waste factor?
Cuts at walls, offcuts too small to reuse, damaged or mismatched batches, and a reserve for later repairs all consume material beyond the literal floor area. No standards body fixes the percentage — it depends on the product, the layout pattern, and the room's shape. Use the preset buttons as starting points and confirm the allowance with the product's installation guide or your installer.
Does the calculator save my measurements?
No. Everything runs in your browser and nothing is uploaded or stored after you close the tab. That also means the calculator works fully offline once the page is loaded.
Can I use this for land or lot size?
Yes for small parcels. The result also shows acres (sq ft ÷ 43,560). For very irregular plots, use the irregular-room tab and split the lot into rectangles using a scaled survey plan. For a house's finished square footage as an appraisal reports it, the rules are different: see the room square footage page for what ANSI Z765-2021 counts and excludes.
Sources and How to Check This Page
- The length and area factors come from NIST Special Publication 811, Appendix B.9.1: 1 ft = 0.3048 m exactly, hence 1 sq ft = 9.290 304 E−02 m², 1 yd = 3 ft, and 1 in = 1/12 ft. Every conversion shown here is arithmetic on those exact factors.
- The international foot and the retirement of the US survey foot are defined in 85 FR 62698, which fixes the foot at 0.3048 m and deprecates the survey foot as of December 31, 2022. This calculator uses the international foot throughout.
- What counts as a home's finished square footage — exterior wall surfaces, garages excluded, unfinished areas excluded — is set by ANSI Z765-2021. The standard's development secretariat publishes the scope and editions at homeinnovation.com/z765, and the Appraisal Institute adoption notice names the Z765-2021 edition. Full quotes are on the room page.
- Every number on this page can be re-derived in a minute: 120 in ÷ 12 = 10 ft, 12 × 10 = 120; 120 × 0.09290304 = 11.15 m²; 120 ÷ 9 = 13.33 sq yd; 120 ÷ 43,560 = 0.0028 acre; 120 × 144 = 17,280 sq in; 120 × 1.10 = 132 sq ft, and 132 × $4.50 = $594.00.
- What this calculator does not do: accept a combined feet-and-inches input, name or label rooms, store or share your entries, compute perimeter, solve backwards from a known area, or price a job from anything but the per-square-foot figure you type. Claims about waste percentages, paint spread, and material cover rates on this site are example practice values, not manufacturer specifications.
Embed This Calculator
Run a flooring blog, a contractor site, or a real-estate portal? You can embed this calculator on your own website with a single copy-paste snippet — it keeps working client-side, with your visitors' measurements never leaving their browser.