Room size calculator
Enter length, width and ceiling height to get the floor area, perimeter, wall area and volume of a room. We also check the US International Residential Code (IRC) minimums.
See your design as an AI render — free- Perimeter
- 44 ft
- Wall area
- 352 sq ft
- Volume
- 960 cu ft
- Passes · US, residential — IRC R304.1: habitable room of at least 70 sq ft (6.5 m²)
- Passes · US, residential — IRC R304.2: no side under 7 ft (2.13 m)
- Passes · US, residential — IRC R305.1: ceiling height of at least 7 ft (2.13 m)
Quick reference only. Always check your country's and city's code before signing off a design.
See this room furnished
Upload a photo of the room, empty or not, and RendScene returns it furnished in the style you choose.
5 free renders · no credit card
How to work out room size
Three measurements are enough: length, width and ceiling height.
- 1
Floor area
Length × width. A 12 × 10 ft bedroom is 120 sq ft.
- 2
Perimeter
2 × (length + width): 2 × (12 + 10) = 44 ft. That is what you buy baseboard and crown molding by.
- 3
Wall area
Perimeter × ceiling height: 44 × 8 = 352 sq ft, without taking out doors and windows. For paint, use the paint calculator.
- 4
Volume
Area × ceiling height: 120 × 8 = 960 cu ft. Volume is what HVAC and ventilation sizing start from.
US residential code minimums (IRC)
The same rules the calculator checks. Every country and city has its own code.
| Rule | Minimum | Notes |
|---|---|---|
| IRC R304.1 — area | 70 sq ft (6.5 m²) | Habitable rooms; kitchens are exempt |
| IRC R304.2 — smallest side | 7 ft (2.13 m) | In any horizontal direction; kitchens are exempt |
| IRC R305.1 — ceiling height | 7 ft (2.13 m) | Habitable space, hallways and basements with those uses |
Frequently asked questions
More free calculators
Design
- Scale calculatorDrawing size to real size and back, at 1:100, 1:50 or 1/4" = 1'-0".
- Floor area ratioMaximum floor area from a zoning FAR, or the FAR of a design.
- Stair calculatorRisers, treads, angle and total run of a stair, with Blondel's rule.
- Ramp slope calculatorLength, grade and landings of a ramp for a given rise.
- Roof pitch calculatorRoof pitch as X/12, degrees and percent, with ridge height and roof area.
- Parking ratio calculatorParking spaces per floor area and the lot area they take up.
Building and materials
- Square footage calculatorArea of rectangles, triangles, circles and trapezoids in sq ft, m² and acres.
- Square meter calculatorSquare meters from length × width, plus m² to sq ft, hectares and acres.
- Paint calculatorGallons or liters of paint for walls and ceiling, minus doors and windows.
- Tile calculatorTiles and boxes for a floor or wall, with grout joint and waste.
- Drywall calculatorDrywall sheets for walls and ceiling, minus doors and windows.
- Insulation calculatorInsulation thickness to reach a target R-value or RSI, by material.
- Brick calculatorBricks per sq ft and the total for a wall, with mortar joint and waste.
- Board foot calculatorLumber volume in board feet and m³, per piece and per order.
From drawing to render in minutes
Upload a floor plan, a sketch or a screenshot of your 3D model and get a photorealistic image that stays faithful to what you drew.
No credit card required