Floor & Room Calculators
These floor and room calculators cover the surfaces, sizes and spaces of a room: its air volume and wall area, carpet and built-up area, drawing scale, furniture clearances, stairs, ramps, corridors and doors. Each one works in metric and imperial, shows its formula with your numbers, and lets you change every assumption.
In this section
- Room Volume CalculatorWork out a room’s volume in m³ and ft³ from width, length and ceiling height, including sloped ceilings and L-shaped rooms, with the formula shown step by step.
- Net Wall Area Calculator for Plaster, Tiles and FinishesFind the net wall area of a room for plaster, tiles and other finishes, less doors, windows and skirting, with any finish above the ceiling, in m² and sq ft.
- Window-to-Wall Ratio CalculatorCalculate window-to-wall ratio for one wall, a whole facade or a room, plus window-to-floor ratio, from window and wall sizes in metric or imperial units.
- Carpet Area CalculatorAdd up a flat’s rooms to get its carpet area in sq ft and m², under the area convention you choose, with balconies and internal walls shown separately.
- Super Built-up Area CalculatorConvert between super built-up, built-up and carpet area with your own loading and wall percentages. See how much of a listed flat size is usable floor.
- Floor Plan Scale CalculatorConvert between drawing and real sizes at any floor plan scale, find the scale from a known dimension, and pick a scale that fits your plan on A4, A3 or Letter.
- Furniture Clearance CalculatorAdd the space you need around a bed, dining table, sofa, desk or wardrobe and see the floor area it takes and the smallest room it fits, in metric and imperial.
- Bedroom Size CalculatorFind the smallest bedroom that fits your bed, nightstands and wardrobe with space to walk, or check your room, in feet and meters, then open it in the editor.
- Living Room Size CalculatorWork out the living room size your sofa, armchairs, coffee table and TV unit need with walkways, or check the room you have, in metric and imperial units.
- Kitchen Work Triangle CalculatorMeasure the legs between sink, hob and fridge, see the triangle’s total and each leg against ranges you set, and spot an island in the way. Metric and imperial.
- Staircase CalculatorWork out the number of steps, riser height, tread depth, total run and pitch of a straight stair from floor-to-floor height, using limits from your local rules.
- Ramp Slope CalculatorConvert a ramp’s rise and run to slope percent, 1:n ratio and angle, or find the length you need for a rise at the maximum slope you enter, including landings.
- Corridor Width CalculatorFind a hallway’s clear width after radiators, handrails and trim, compare it with your target, and check whether a sofa or bed turns the corner flat.
- Door Clearance CalculatorSee the space a hinged door sweeps, its clear opening width when open, and how far it opens before hitting furniture or a wall, in metric and imperial.
How these calculators work
Type sizes the way you would read them off a tape: 4.2, 420 cm, 13' 9" or 165 in. Results update as you type and always show both unit systems. Under each result, “How this was calculated” lists the formula and every step with your numbers.
Any figure that is not a plain definition (a threshold, a clearance, a target) is shown as an editable assumption with a note on where the default comes from. Reset puts the example back, Copy result gives you plain text with the steps, and Print puts the inputs, assumptions and results on one page.
Working with the floor plan editor
Calculators that end in a room size have a “Design this room” button. Rooms in the editor are measured to the middle of their walls, so when you entered inside sizes the room opens one wall thickness bigger each way and its inside matches your numbers.
Nothing you type is saved or sent anywhere. A share link carries your inputs in the part of the address after the #, which stays in your browser.
More area and layout tools
- Room size calculatorFloor area and perimeter of a rectangular room.
- Square footage calculatorAdd up rectangles and L-shapes in sq ft and m².
- Floor area calculatorThe total floor area of a home, room by room.
- Room dimension calculatorWidth and length for a room of a given area.
- Furniture layout plannerCheck that your furniture fits with space to walk.
Frequently asked questions
Do these calculators work in feet and inches?
Yes. Switch to imperial and type sizes such as 13' 9" or 165 in; you can also type metric values in imperial mode. Every result shows both systems.
Are my measurements stored?
No. The calculations run in your browser. Only your choice of metric or imperial is remembered on this device; a share link keeps the inputs in the link itself.
Can I use a result in the floor plan editor?
Where the result is a room, yes: “Design this room” opens a new project with that room drawn, in the units you chose.
Ready to plan your space?
It is free, runs in your browser and needs no account. Projects are saved privately on this device.