Irregular Shape Square Footage Calculator
Calculate square footage for irregular shapes by breaking them into simple rectangles, triangles, and circles. The multi-segment calculator handles up to 20 individual sections.
Irregular Area Calculator
Divide and conquer
Any irregular shape can be approximated by combining rectangles, triangles, and circle segments. The trick is sketching the layout and breaking it into simple pieces with no overlaps and no gaps.
For an L-shaped room, draw a horizontal line that splits the L into two rectangles. Measure each rectangle separately, then add. For a T-shape, two rectangles. For an octagon (8-sided), one central rectangle plus four corner triangles.
Common irregular layouts
L-shape: 2 rectangles. Most common in kitchens and great rooms. Total = (L1 × W1) + (L2 × W2).
T-shape: 2 rectangles. Top of T is one rectangle; the stem is another. Be careful not to double-count the area where they overlap.
Bay window or alcove: main rectangle + small rectangle for the alcove. If the alcove is angled (45°), use a trapezoid or two triangles.
Round-end rectangle: one rectangle + two semicircles at the ends. Common in stadiums, lozenge-shaped patios, and some garden beds.
Pro tips
Sketch first, measure second
Always draw the floor plan before pulling out a tape. Mark every dimension on the sketch as you measure. Memory is unreliable.
Look for the natural break
Most rooms have a natural rectangular break - a wall jog, a column, a chimney. Use those as your section dividers.
Check by perimeter
The sum of your sections' areas should match the room's actual area. As a sanity check, walk the perimeter and see if your dimensions add up.
Use approximation for curves
For a curved wall or organic boundary, approximate with 2-3 rectangles or a series of trapezoids. 95% accurate is usually plenty for material estimates.