AJ Designer

Square Footage Calculator

Solution

—

Area equals length times width.

Share:

Rectangle Square Footage

The most common room shape. Multiply length by width — both in feet — to get area in square feet. A 12 ft × 15 ft bedroom is 12 × 15 = 180 sq ft.

A = L × W

Square Room

A square room has only one dimension. Square the side length: a 10 ft × 10 ft room is 10² = 100 sq ft.

A = s²

Triangular Floor Area

Works for both right triangles and any triangle, as long as 'height' is the perpendicular distance from the base to the opposite vertex (not the slanted side). A right triangle with 6 ft and 8 ft legs is 6 × 8 / 2 = 24 sq ft.

A = (1/2) × base × height

Circular Floor (Radius)

For round rooms and gazebos. A radius of 10 ft gives A = π × 100 ≈ 314.16 sq ft.

A = π × r²

Circular Floor (Diameter)

Same as the radius formula, but takes the diameter directly. A 20 ft diameter circle = π × (10)² ≈ 314.16 sq ft.

A = π × (d / 2)²

Trapezoidal Floor Area

For rooms with two parallel sides of different lengths. With a = 10 ft, b = 14 ft, and h = 8 ft perpendicular height between them: A = ((10 + 14) / 2) × 8 = 96 sq ft.

A = ((a + b) / 2) × h

Multi-Room Total

Sum the rectangular areas of every room. For irregular L-shaped or T-shaped rooms, divide the floor plan into rectangles and add one row per rectangle. Closets and alcoves are added the same way.

A_total = Σ (Lᵢ × Wᵢ)

How It Works

Square footage is the total floor area of a room (or set of rooms) expressed in square feet. Pick the room shape that fits, measure in feet, and the calculator returns area in sq ft, sq meters, and sq yards. Rectangles dominate residential floor plans (A = L × W), but circles cover gazebos and rotundas (A = πr²), triangles cover attic dormers and corner rooms (A = ½ · b · h), and trapezoids cover rooms with one angled wall (A = ((a + b) / 2) · h). For irregular floor plans — L-shapes, T-shapes, rooms with bay windows or built-ins — use the multi-room mode and divide the plan into rectangles. The conversions are simple: 1 sq yard = 9 sq ft (a 3 ft × 3 ft square), and 1 sq meter ≈ 10.7639 sq ft. To convert sq ft to sq meters, divide by 10.7639.

Example Problem

A two-bedroom apartment has a 16 ft × 20 ft living room, a 12 ft × 14 ft kitchen, and a 12 ft × 12 ft bedroom. Compute the total floor area for a listing and convert to square meters.

  1. Identify each room as a rectangle, since all three are right-angled.
  2. Compute the living room area: 16 ft × 20 ft = 320 sq ft.
  3. Compute the kitchen area: 12 ft × 14 ft = 168 sq ft.
  4. Compute the bedroom area: 12 ft × 12 ft = 144 sq ft.
  5. Sum the rooms: 320 + 168 + 144 = 632 sq ft total floor area.
  6. Convert to square meters: 632 sq ft ÷ 10.7639 ≈ 58.71 m². Convert to square yards: 632 ÷ 9 ≈ 70.22 sq yd.

Real-estate listings typically use Gross Living Area (GLA), measured from the outside of exterior walls. The number from interior measurements like these runs about 5-10% lower than GLA. Add a small allowance if you're sizing a listing for MLS comp purposes.

Key Concepts

Three practical points trip people up most often. First, units in must match units out. If you measure in inches but want square feet, convert lengths to feet first (divide by 12). Multiplying inches together gives square inches, not square feet — and a 144 sq in floor is a 1 sq ft floor, not 144 sq ft. Second, alcoves and built-ins. Closets, walk-ins, pantries, and built-in benches are usually counted as part of the room's square footage for flooring and paint orders, but real-estate Gross Living Area rules vary by market — when in doubt, count anything you'd walk on, sand, or carpet. Third, walls do not count. Square footage is the floor footprint, not the perimeter or wall area. Painters use linear feet of wall × ceiling height for paint; that's a different calculation. For flooring (carpet, hardwood, tile, vinyl), it's strictly the floor area in this calculator, plus a 5-10% waste factor when ordering.

Applications

  • Flooring orders — carpet, hardwood, laminate, tile, and vinyl are all sold by the square foot or square yard. Compute the area, add a 5-10% waste factor (more for diagonal patterns or rooms with many cuts), and that's the order quantity.
  • Paint coverage — a gallon of interior paint covers roughly 350-400 sq ft per coat. The floor area helps size paint for floors and stain for decks; for walls, multiply perimeter by ceiling height instead.
  • Real-estate listings — the square footage on an MLS or Zillow listing is Gross Living Area, the sum of all finished, heated rooms. Square footage is the single most-cited number when comparing comps.
  • Property taxes and assessments — county assessors price land and improvements partly on square footage. A reassessment after a remodel often turns on the addition's square footage.
  • HVAC sizing — air conditioner and furnace sizing rules of thumb start from heated square footage (typically 20-30 BTUs per sq ft for cooling, depending on climate and insulation).
  • Rent and lease pricing — commercial leases are quoted per square foot per year, and apartments are increasingly compared on $/sq ft to control for size differences.
  • Lot and yard planning — fencing, sod, landscaping fabric, and gravel are priced per sq ft or sq yd. Compute the planted/paved area before ordering material.

Common Mistakes

  • Mixing units mid-calculation — measuring length in feet and width in inches gives a number that's neither sq ft nor sq in. Pick one unit, convert everything to it, then multiply.
  • Treating a slanted side as the triangle height — a right triangle with legs 6 ft and 8 ft has hypotenuse 10 ft, but the area uses the 6 and 8 (the legs), not the 10. For non-right triangles, drop a perpendicular from the apex to the base to find the true height.
  • Forgetting to subtract or add irregular features — bay windows, alcoves, and closets are usually added; columns, fireplaces with built-in hearths, and built-in cabinets reduce the floor area for flooring orders (the floor under them is hidden) but are still counted in real-estate GLA.
  • Using diameter instead of radius in circle area — A = π × r², not π × d². If you only have the diameter, divide by 2 first (or use the diameter mode in this calculator, which does it for you).
  • Multiplying linear feet by 9 to get square yards — square yards convert by dividing by 9, not multiplying. 90 sq ft is 10 sq yd, not 810. The factor 9 = 3² comes from 1 yard = 3 feet.
  • Confusing sq ft and ft² with linear feet — flooring is square feet (area), trim and baseboards are linear feet (length). A 10 ft × 12 ft room has 120 sq ft of floor and 44 linear feet of baseboard.

Frequently Asked Questions

How do I calculate square footage?

For a rectangular room, multiply length by width — both measured in feet. A 12 ft × 15 ft room is 12 × 15 = 180 sq ft. For non-rectangular shapes, use the matching formula: A = s² for a square, A = ½ · base · height for a triangle, A = πr² for a circle, A = ((a + b)/2) · h for a trapezoid. For irregular floor plans, divide the plan into rectangles and sum the rectangular areas.

What is the formula for square footage?

The basic rectangular formula is A = L × W, with length and width in feet and area in square feet. The full set of room-shape formulas is: rectangle A = L × W, square A = s², triangle A = ½ × base × height, circle A = π × r², trapezoid A = ((a + b)/2) × h. For multi-room totals, sum the per-room areas: A_total = Σ (Lᵢ × Wᵢ).

What's the difference between square feet and square yards?

Square yards are larger: 1 square yard = 9 square feet (a 3 ft × 3 ft square). To convert, divide square feet by 9 to get square yards. For example, 180 sq ft ÷ 9 = 20 sq yd. Carpet and sod are often sold by the square yard; flooring tile and hardwood are usually sold by the square foot.

How do I calculate the square footage of multiple rooms?

Calculate the area of each room individually (length × width for rectangles), then add them all together. For example, a 320 sq ft living room + 168 sq ft kitchen + 144 sq ft bedroom = 632 sq ft total. Use the multi-room mode in this calculator to add one row per room; the calculator sums the rectangles automatically and skips any blank rows.

Does square footage include closets, alcoves, and bathrooms?

For flooring, paint, and material orders — yes, count anything you'd walk on, sand, or cover. For real-estate Gross Living Area (GLA), the rules are stricter: only finished, heated, and accessible-from-the-living-area space counts. Closets and bathrooms count if they're in the heated envelope; unfinished basements, attics, and garages don't, even if they have a finished floor.

How many square feet are in a square meter?

1 square meter ≈ 10.7639 square feet. To convert square feet to square meters, divide by 10.7639. For example, 1000 sq ft ÷ 10.7639 ≈ 92.90 m². To convert square meters to square feet, multiply by 10.7639. The exact factor is (1/0.3048)² because 1 meter = 1/0.3048 feet.

How do I calculate flooring square footage?

Measure each room's length and width in feet, multiply to get square feet, and sum all rooms. Then add a 5-10% waste factor for cuts, pattern matching, and future repairs (closer to 15% for tile in diagonal patterns or rooms with many obstacles). For a 632 sq ft area, order 695-700 sq ft (about 10% extra). Save a few extra planks/tiles to match future repairs.

How do I calculate the square footage of an irregularly shaped room?

Divide the floor plan into simple shapes — usually rectangles, sometimes a triangle or trapezoid for an angled wall — then sum the areas. For an L-shaped room, draw a line splitting it into two rectangles, compute each separately, and add them. The multi-room mode in this calculator is built for exactly this workflow: add one row per rectangle.

Reference: NIST SP 811 — Guide for the Use of the International System of Units (SI). ANSI Z765-2021 — Square Footage Method for Calculating: Single-Family Residential, the dominant US standard for real-estate GLA measurement.

Worked Examples

Flooring

How many square feet of hardwood for a 16 × 20 ft living room?

A rectangular living room is 16 ft long and 20 ft wide. Find the floor area to size the hardwood order.

  • Knowns: L = 16 ft, W = 20 ft.
  • Formula: A = L × W.
  • A = 16 × 20 = 320 sq ft.
  • Convert: 320 sq ft ÷ 9 ≈ 35.56 sq yd, 320 ÷ 10.7639 ≈ 29.73 m².

Area = 320 sq ft (≈ 35.56 sq yd, 29.73 m²)

Order 10% extra (≈ 352 sq ft) to cover cuts, pattern matching, and future repairs — a standard flooring waste factor.

Paint Job

How big is a circular gazebo with a 12 ft diameter (for stain coverage)?

A round gazebo deck has a 12 ft diameter. Compute floor area to estimate stain or sealer needed (one gallon typically covers ~250 sq ft).

  • Known: d = 12 ft, so r = 6 ft.
  • Formula: A = π × r².
  • A = π × 36 ≈ 113.1 sq ft.
  • Stain: 113.1 ÷ 250 ≈ 0.45 gallon for one coat; buy 1 gallon to cover two coats.

Area ≈ 113.10 sq ft (≈ 10.51 m², 12.57 sq yd)

Stain coverage is more porous than paint on smooth surfaces — for raw lumber, drop to ~150 sq ft per gallon and budget accordingly.

Whole House

What's the total square footage of a 3-room apartment for a listing?

A two-bedroom apartment: 16 × 20 ft living room, 12 × 14 ft kitchen, 12 × 12 ft bedroom. Sum to get the marketed square footage.

  • Living room: 16 × 20 = 320 sq ft.
  • Kitchen: 12 × 14 = 168 sq ft.
  • Bedroom: 12 × 12 = 144 sq ft.
  • Total = 320 + 168 + 144 = 632 sq ft.
  • Convert: 632 ÷ 9 ≈ 70.22 sq yd, 632 ÷ 10.7639 ≈ 58.71 m².

Total ≈ 632 sq ft (≈ 70.22 sq yd, 58.71 m²)

Real-estate listings typically advertise GLA (gross living area) — finished, conditioned space measured from exterior walls. Add ~10% to interior-wall floor areas to approximate the listed figure.

Square Footage Formulas

Square footage is just "area" with feet as the working unit. Each room shape has its own area formula:

Rectangle: A = L × W
Square: A = s²
Triangle: A = ½ × base × height
Circle (radius): A = π × r²
Circle (diameter): A = π × (d / 2)²
Trapezoid: A = ((a + b) / 2) × h
Multi-room: A_total = Σ (Lᵢ × Wᵢ)

Where:

  • A — floor area (in sq ft when all inputs are in feet)
  • L, W — length and width of a rectangular room
  • s — side length of a square room
  • base, height — base of a triangle and the perpendicular distance from base to apex (NOT the slanted side)
  • r, d — radius or diameter of a circular floor
  • a, b, h — the two parallel sides of a trapezoid and the perpendicular distance between them

Converting between area units: 1 sq yard = 9 sq ft (exact: 3 ft × 3 ft); 1 sq meter ≈ 10.7639 sq ft. To convert square feet to square meters, divide by 10.7639. To convert square feet to square yards, divide by 9.

Related Calculators

Related Sites