The Odd-Shaped Room Square Footage Calculator finds the floor area of rooms that aren’t simple rectangles. It has four tools: L-shaped rooms, rooms with a bay window, rooms with an angled (cut) corner, and any irregular room entered as a list of corner points.
Odd-Shaped Room Square Footage Calculator
Square footage of L-shaped rooms, rooms with bay windows or angled corners, and any irregular room from its corner points.
The first three subtract or add simple shapes to a rectangle. The corner-points tool uses the shoelace formula, which works for any room with straight walls — just walk around the room and note each corner.
Formula
- L-shaped: A = overall L × overall W − notch length × notch width
- Bay window: A = room + bay; rectangular bay w × d; half-circle π(w/2)² ÷ 2; angled bay (w + front) ÷ 2 × d
- Angled corner: A = L × W − (a × b) ÷ 2; angled wall = √(a² + b²)
- Any shape (shoelace): A = ½ |Σ(xᵢ × yᵢ₊₁ − xᵢ₊₁ × yᵢ)|
How the Calculation Works
Step 1: Pick the tool that matches the room shape.
Step 2: Enter the overall dimensions and the part that is added or missing.
Step 3: For the corner tool, list corners in order (clockwise or counter-clockwise) starting from 0, 0.
Example Calculation
L-shaped room
Given: 20 × 15 ft overall with an 8 × 5 ft notch
A = 300 − 40 = 260 ft²; perimeter = 70 ft
Room with an angled bay
Given: 15 × 12 ft room, bay 8 ft wide at the wall, 5 ft at the front, 2 ft deep
Bay = (8 + 5) ÷ 2 × 2 = 13 ft²; total = 180 + 13 = 193 ft²
Angled corner
Given: 15 × 12 ft room with a 3 × 3 ft corner cut
A = 180 − 4.5 = 175.5 ft²; angled wall ≈ 4.24 ft
Any shape
Corners: (0,0), (16,0), (16,10), (10,10), (10,14), (0,14)
A = 200 ft²; perimeter = 60 ft
Dimensions Explained
- For the L-shape, the notch is the rectangle “missing” from the overall box.
- For corner points, measure along two perpendicular reference walls; the shoelace formula needs the corners in order around the room.
- Curved walls other than a half-circle bay can be approximated with several short straight segments.
Frequently Asked Questions
How do I calculate square footage of an irregular room?
Split it into rectangles and triangles and add them, or enter its corner points to use the shoelace formula.
How do I calculate an L-shaped room?
Overall rectangle minus the missing corner rectangle — or add the two rectangles that make up the L.
How do I include a bay window?
Add the bay’s area to the main rectangle; an angled bay is a trapezoid.
Does the order of corners matter?
Yes — enter them in sequence around the room; either direction works.
Do I include closets?
Include them if the floor covering continues into them.
