Room Area Calculator

How do I calculate the total floor area of a house with multiple rooms?

Work out each room’s floor area from its shape, then add them all up. AnyTool Room Area Calculator does this live: add a room, pick its shape — rectangle (length × width), L-shape (overall box minus a corner notch), circle (πr²), triangle (½ × base × height) or trapezoid (½ × (a + b) × height) — type the dimensions, and add another room for the next space. It sums every room into one grand total floor area and shows it in m², ft² and square yards at once (plus roofing squares), with a perimeter where a closed boundary makes sense and an optional price per area for a quick flooring or rent budget. It is FLOOR area, not wall area — for painting, use wall area instead. Everything is computed in your browser; nothing is uploaded.

Per-room area by shape, then total = sum of all rooms
Rectangle L×W · L-shape box−notch · circle πr² · triangle ½bh · trapezoid ½(a+b)h
Total shown in m², ft² and yd² (and 100 ft² roofing squares)
Floor area (footprint), not wall area — measure to the widest points
100% in your browser — no upload, no signup, works offline

What is

Floor area (room area)

The size of the floor footprint you walk on, measured per room from its shape and then summed across every room to give a total floor area for a whole home. A rectangular room is length × width; an L-shaped room is its overall bounding box minus the rectangular corner notch; a circular bay is π × radius²; a triangular corner is half the base times the height; and a trapezoidal space is half the sum of the two parallel sides times the height. Floor area is the basis for flooring quantities, property listings, gross internal area and rent-per-square-foot, and is distinct from wall area (perimeter × height) used for painting. It is the bare footprint, so it does not subtract internal walls, columns or fitted furniture.

Calculators

Related terms

Square footageTotal floor areaL-shaped roomGross internal areaWall areaSquare metres

Frequently Asked Questions

An L-shaped room is just a rectangle with a corner removed, so there are two equivalent ways to measure it. You can divide the L into two rectangles, work out each one’s length × width, and add them together. Or you can measure the overall bounding box (the full length and full width as if the corner were filled in) and subtract the missing rectangular notch: area = (length × width) − (notch length × notch width). For example, a 5 m × 4 m box is 20 m²; removing a 2 m × 1.5 m corner (3 m²) leaves 17 m². AnyTool’s Room Area Calculator uses the box-minus-notch method for L-shape rooms and lets you add other odd shapes as separate rectangles, summing everything into a total.

Split it into two rectangles and add them, or take the overall bounding box and subtract the corner notch. A 5 × 4 m box minus a 2 × 1.5 m notch is 20 − 3 = 17 m².

Total house square footage is the sum of every room’s floor area. Measure each room to its widest points, work out its area from its shape (length × width for a rectangle, box minus notch for an L-shape, and the matching formula for circular, triangular or trapezoidal spaces), and add every room together — don’t forget hallways, closets, landings and stairwells, which all count. AnyTool’s Room Area Calculator keeps a running total: add a room, pick its shape, enter the dimensions, then add the next room, and it shows the grand total in m², ft² and square yards with a per-room breakdown. It is the bare floor footprint, so it does not subtract internal walls or fitted furniture, and local rules on what counts as “living area” vary.

Measure each room’s length and width (or its shape), find each area, and add them all together — including hallways, closets and stairwells. Repeat for every room and sum the totals.

Floor area is the horizontal footprint of a room — what you cover with flooring or quote for a listing — found from the floor’s shape, for example length × width for a rectangle. Wall area is the vertical surface of the walls you would paint or wallpaper, found as the room’s perimeter multiplied by the wall height, usually with doors and windows deducted. They answer different questions: you order carpet by floor area but paint by wall area. AnyTool’s Room Area Calculator computes floor area (and perimeter, which is the input to wall area); for paint quantities, use the Paint Calculator, which works from wall area and deducts openings.

Floor area is the footprint you walk on (length × width of the floor). Wall area is the vertical surface you paint (perimeter × height). This tool gives floor area; for painting use wall area.

One square foot equals 0.09290304 square metres, and one square metre equals 10.7639 square feet, so to convert square feet to square metres multiply by about 0.0929, and to go the other way multiply by about 10.7639. For square yards, there are 9 square feet in a square yard, and one square metre is about 1.196 square yards. AnyTool’s Room Area Calculator shows the total floor area in square metres, square feet AND square yards at the same time (plus roofing “squares” of 100 ft²), so you don’t have to convert by hand — just switch between metric and imperial input and read every unit at once.

Multiply square feet by 0.0929 to get square metres, or multiply square metres by 10.7639 to get square feet. A 130 ft² room is about 12.1 m².

Calculate each room’s floor area from its shape — rectangle, L-shape (box minus notch), circle, triangle or trapezoid — and sum every room into a grand total floor area for a whole home, shown in m², ft² and square yards with perimeter and an optional cost, all computed live in your browser.

Features

Per-room shapes: rectangle, L-shape, circle, triangle, trapezoid
Multiple rooms summed into one total floor area
Total in m², ft² and yd² (plus 100 ft² roofing squares)
Perimeter where a closed boundary is meaningful; optional price per area
Floor area not wall area; honest measure-to-the-widest-points caveat — 100% client-side

PriceFree

CategoryCalculator

PlatformAll (browser-based)

PrivacyThe room shapes, dimensions and prices you enter never leave your device

Input: Per-room shape, Room dimensions (length, width, radius, base, height, sides, notch), Metric or imperial, Optional price per m²/ft²

Output: Per-room floor area, Total floor area (m², ft², yd²), Roofing squares, Perimeter, Optional total cost

Detailed Explanation

Methodology

How the Room Area Calculator Works

The calculator builds a list of rooms and sums their floor areas into a grand total. Each room is assigned a shape and the area is computed from the matching formula: a rectangle is length × width; an L-shape is its overall bounding box minus a rectangular corner notch (length × width − notchLength × notchWidth); a circle is π × radius²; a triangle is ½ × base × height (with a Heron-of-Alexandria fallback from three sides); and a trapezoid is ½ × (a + b) × height, where a and b are the parallel sides. Incomplete or non-positive rooms contribute zero rather than breaking the total. The active-unit total is then converted so the result is shown in square metres, square feet and square yards simultaneously, plus roofing “squares” of 100 ft², with a perimeter accumulated for the shapes that have a meaningful closed boundary.

Total floor area = Σ(per-room area by shape)
Rectangle L×W · L-shape box−notch · circle πr² · triangle ½bh (or Heron) · trapezoid ½(a+b)h
1 ft² = 0.09290304 m²; 1 m² = 10.7639 ft²; 9 ft² = 1 yd²
Roofing square = 100 ft²
All math is client-side JavaScript with no server round-trip

Use Cases

Per-Room Areas and Whole-Home Totals

The tool is built for the home and renovation use case rather than abstract geometry: it answers how big each room is and what the total floor area of the whole place is. Because every room carries its own shape, a real home — rectangular bedrooms, an L-shaped living/dining space, a round bay window, a triangular loft corner, a trapezoidal attic — can be measured room by room and summed. The total floor area is the figure used for flooring quantities, property listings, gross internal area, and rent or value per square foot, while a per-room breakdown shows where the space goes. An optional price per square metre or foot turns the total into a quick flooring or rent budget.

A list of rooms, each with its own shape and dimensions
Grand total floor area plus a per-room breakdown
Used for flooring, listings, gross internal area, rent/value per ft²
Optional price per area gives an instant budget
Add hallways, closets and stairwells as their own rooms

Limitations

Why It Is Floor Area, Not Wall Area

The result is the bare floor footprint you walk on, and it is only as accurate as the measurements entered. Real rooms are rarely perfect rectangles, so measure to the widest points and add alcoves and bay windows as their own rooms; for an L-shape, set the overall box and the corner notch. The total does not subtract internal walls, columns, chimney breasts, kitchen units or fitted furniture, all of which reduce usable area, and it does not add a flooring waste factor. Crucially this is floor area, not wall area: painting is estimated from wall area (perimeter × height) with openings deducted, so a paint job should use a wall-area calculator instead. Standards for what counts as living area or gross internal area also differ by region, so confirm against the rule a sale, valuation or permit requires.

Floor area (footprint), not wall area (perimeter × height)
Measure to widest points; add alcoves and bays as rooms
Does not subtract internal walls, columns or fitted furniture
No flooring waste factor — add one for ordering material
Living-area / GIA standards vary by region

Privacy & Security

Privacy and Offline Use

All computation runs in the browser, so the room shapes, dimensions and prices you enter are never sent to a server, there is no account or tracking, and the page works offline after first load. The calculator is built on a shared, unit-tested room-area engine, so its per-room formulas and unit conversions behave consistently across metric and imperial, and the full result — every room’s area, the grand total in m², ft² and yd², the perimeter and any cost — can be copied to the clipboard with one tap.

Room area: in-browser (AnyTool) vs typical online square-footage calculators
Capability	AnyTool	Typical online square-footage calculators
Processing	Runs in your browser	Often server-side
Rooms	Many rooms, summed to a total	Often one room at a time
Per-room shapes	Rectangle, L, circle, triangle, trapezoid	Often rectangle only
L-shape method	Overall box minus a notch	Manual split
Units shown	m², ft² and yd² at once	Usually one unit
Perimeter	Where a boundary is meaningful	Rarely
Optional cost	Price per area for a budget	Sometimes
Floor vs wall area	Explicitly floor area, with guidance	Often unclear
Works offline	Yes (PWA)	No
Cost / signup	Free, no signup	Often ad-heavy or gated

AnyTool computes the floor area locally and uploads nothing. Comparison as of June 2026.

Cite This Page

Title: Room Area Calculator (per-room floor area by shape and the total floor area of a whole home)
Author: AnyTool
Published: January 1, 2026
Modified: February 8, 2026
Section: Calculators
URL: https://www.anytool.tech/room-area-calculator

Formatted Citation

AnyTool. "Room Area Calculator (per-room floor area by shape and the total floor area of a whole home)." AnyTool, January 1, 2026. https://www.anytool.tech/room-area-calculator

A privacy-first, 100% client-side room area calculator for the home and renovation use case: it measures the floor area of each room from its shape and sums every room into a grand total floor area for a whole property. Each room is assigned a shape and computed from the matching formula — a rectangle is length × width, an L-shape is its overall bounding box minus a rectangular corner notch, a circle is π × radius², a triangle is half the base times the height (with a Heron three-side fallback), and a trapezoid is half the sum of the two parallel sides times the height — and incomplete rooms contribute zero so the running total never breaks. The active-unit total is converted so it is shown in square metres, square feet and square yards at once (plus roofing squares of 100 ft²), with a perimeter accumulated for the rectangle, L-shape and circle rooms where a closed boundary is meaningful, and an optional price per square metre or foot gives a quick flooring or rent budget; it works in metric (m, m²) or imperial (ft, ft²) across multiple currencies. Its core honesty is that this is the bare floor footprint, not wall area: it is only as accurate as the tape, so users should measure to the widest points and add alcoves and bays as their own rooms, and it deliberately does not subtract internal walls, columns or fitted furniture, add a flooring waste factor, or replace a wall-area paint estimate — and living-area standards vary by region. Every calculation is a pure, unit-tested function that runs entirely in the browser, uploading nothing and working offline.