Room Size Calculator
Type a room’s width and length into this room size calculator to get its floor area and perimeter in feet and meters. Then open it in the editor to add doors, windows and furniture. Know the area and need the sides? Use the room dimension calculator.
Room size calculator
Meters, e.g. 4.2, 420 cm or 4200 mm
Meters, e.g. 4.2, 420 cm or 4200 mm
- Area
- 14.00 m²
- 150.7 sq ft
- Perimeter
- 15.00 m
- 49′ 3″
A room 4.00 m (13′ 1″) wide and 3.50 m (11′ 6″) long has a floor area of 14.00 m² (150.7 sq ft).
For scale, using the editor’s furniture sizes
- Double bed (1.60 m × 2.00 m): 23% of this floor
- Sofa (2.10 m × 0.90 m): 14% of this floor
- Dining table (1.60 m × 0.90 m): 10% of this floor
How this was calculated
- Area = width × length
- Perimeter = 2 × (width + length)
- Area = 4.00 m × 3.50 m = 14.00 m²
- Perimeter = 2 × (4.00 m + 3.50 m) = 15.00 m
How to use it
Pick your units
Choose metric or imperial. Results always show both, with your choice first.
Enter width and length
A bare number means meters in metric and feet in imperial. You can also type 420 cm, 4200 mm, 13' 9" or 165 in in either mode.
Read area and perimeter
Areas are shown to 0.01 m² and 0.1 sq ft; lengths to the centimeter or the nearest inch.
Design this room
Opens the floor plan editor with a rectangular room of that size already drawn and named, ready for doors, windows and furniture.
Reading the result
Floor area is width times length: a room 4 m by 3.5 m has 14 m² of floor, and a room 12 ft by 11 ft 6 in has 138 sq ft. The perimeter is the distance around the walls, which is what you measure for skirting boards or a picture rail.
Below the result, the calculator compares the room with three pieces from the editor’s furniture library, a double bed, a sofa and a dining table, so you can picture how much of the floor they take up. It shows your own numbers and sets no rule for how big a room should be.
Measuring a room for the calculator
Measure wall to wall at floor level, along the longest clear line you can, and write down both directions before you leave the room. Keep to one unit while you measure; the calculator converts afterwards.
If the room is not a simple rectangle, measure it as several rectangles and add them up with the square footage calculator, which also takes L-shapes.
In the editor, walls are drawn on their center lines, so the room you open from here encloses exactly the width and length you typed and its area matches this result. The clear floor inside is about one wall thickness smaller in each direction.
Common uses
Flooring and rugs
The area is the figure a flooring supplier asks for; check with them how much extra to allow for cuts.
Skirting and trim
The perimeter gives the run of skirting board, before you subtract the door openings.
Comparing rooms
See a room from a listing in the unit you think in: square feet and square meters side by side.
Starting a plan
Open the room in the editor and keep going: doors, windows, furniture and a 3D view.
Frequently asked questions
How do I work out the area of a room?
Multiply the width by the length. Use the same unit for both: meters give square meters and feet give square feet. This calculator does it for you and converts between the two.
How many square feet is a 12 × 12 ft room?
144 sq ft, which is about 13.38 m². In the other direction, a 4 × 4 m room is 16 m², or about 172.2 sq ft.
How many square feet are in a square meter?
One square meter is about 10.764 square feet, and one square foot is exactly 0.09290304 square meters, because a foot is exactly 0.3048 m.
Can I enter feet and inches?
Yes. Type 13' 9", 13ft 9in, 13'9 or 165 in. Fractions such as 9 1/2" work too, and you can type metric values while in imperial mode.
What does “Design this room” do?
It creates a new project in this browser with one rectangular room of your width and length, in the units you chose, and opens it in the editor. Nothing is uploaded.
Are my measurements saved?
No. The calculator works in your browser and forgets the numbers when you leave the page; only your choice of units is remembered. A project you open in the editor is kept in this browser’s storage.
Ready to plan your space?
It is free, runs in your browser and needs no account. Projects are saved privately on this device.