How to measure an L-shaped room step by step
An L-shaped room looks awkward to measure, but it's really two rectangles sharing a corner. The whole job comes down to one decision: where to draw the dividing line. Stand in the room and imagine extending one of the inner walls straight across until it splits the floor into two clean rectangles. Once that line is drawn, each half is an ordinary rectangle you can measure with a tape.
Measure the length and width of the first rectangle in feet and multiply them together — that's its area. Do the same for the second rectangle. Then add the two areas for your total. For a room whose main part is 15 ft by 12 ft (180 sq ft) with an 8 ft by 6 ft leg (48 sq ft), the total is 228 sq ft. If your walls aren't perfectly straight, treat each room section separately and take measurements at floor level where the flooring will actually go.
Which way should you split the L?
Every L can be divided two ways: you can extend one inner wall to make a tall rectangle plus a short one, or extend the other inner wall to make a wide rectangle plus a narrow one. Both are correct, and both give exactly the same total square footage — the geometry guarantees it. Choose the split that gives you the easiest walls to reach with a tape measure and the fewest obstacles like furniture or cabinets.
The one rule that matters is that your two rectangles must not overlap, and together they must cover the entire floor with no gap. If they overlap you'll count some floor twice; if there's a gap you'll come up short. A quick sketch on paper, with each rectangle's dimensions written on it, makes overlaps and gaps obvious before you start multiplying.
When rooms get more complicated
The two-rectangle trick handles a clean L, but real rooms often have closets, alcoves, bay windows, or angled corners. The method still works: keep dividing the space into rectangles until every part of the floor belongs to exactly one rectangle, then add them all. A closet becomes its own small rectangle; a bump-out becomes another.
For spaces with curves, diagonals, or many small jogs, a pure rectangle split gets tedious, and the approach for irregular rooms — breaking the floor into a mix of rectangles and triangles — is the better tool. Whichever shapes you use, the principle never changes: cover the floor with non-overlapping pieces, find each area, and add them up.