Room Perimeter Calculator - Rectangular & Irregular Rooms
Calculate a room's perimeter from length and width, or sum wall segment lengths for an irregular room shape.
ft
ft
Total Perimeter
44.00 ft
Floor Area
120.00 sq ft
How Room Perimeter Is Calculated
For a simple rectangular room, perimeter is twice the sum of length and width. For a room that isn't a clean rectangle — an L-shaped room, a room with a bump-out, or an oddly angled space — switch to Irregular Room mode and enter the length of each wall segment going around the room; the tool adds them all up for you.
Irregular Perimeter = Sum of All Wall Segment Lengths
Example
A 12 ft × 10 ft rectangular room has a perimeter of 2 × (12 + 10) = 44 ft. An L-shaped room with wall segments of 8, 5, 6, and 9 ft has a perimeter of 8 + 5 + 6 + 9 = 28 ft.
Common Use Cases
- Estimating how much baseboard or trim molding to buy for a room.
- Figuring out crown molding or wallpaper border length.
- Planning fencing-style perimeter materials around an irregular space.
- Double-checking a contractor's quoted linear footage before ordering materials.
FAQs
Should I subtract doorways and openings from the perimeter?
For baseboard or trim, yes — subtract the width of any doorways or open archways, since trim isn't installed across an opening. This tool gives the full wall perimeter; deduct openings separately for an exact material order.
How do I measure an irregular room?
Walk the room's perimeter and measure each straight wall segment one at a time, in order, then enter each length as its own row in Irregular Room mode. The tool sums every segment into a total perimeter.
Does this calculate floor area too?
In Rectangle mode, yes — the area (length × width) is shown alongside the perimeter. Irregular mode only totals the perimeter, since area for a non-rectangular shape needs more than just the outer wall lengths.