How to Measure an L-Shaped Room for Flooring

Updated November 1, 2026

An L-shaped floor is two rectangles. Sketch the L, cut it once at the inside corner, multiply each rectangle, and add the square feet. The Flooring Calculator accepts one length and one width. Its room count only repeats that same rectangle. It will not take the L in one pass. Waste percent and the round-up to full boxes come after this measurement, on Flooring Square Footage With Waste Allowance.

Sketch the L before you add

Draw the room the way the flooring will stop: walls, a jog, and the inside corner where the two legs meet. A diagonal tape reading is not a side. Measure each outside edge in feet, and write the number on the sketch next to that edge.

Pick one cut through the inside corner so the two rectangles share that edge and nothing else. The corner square belongs to one rectangle. If both rectangles include it, the total is long by that square and you will buy flooring for floor you do not have.

A 12 by 10 main area and an 8 by 6 leg

One way to draw this L: a main rectangle 12 feet by 10 feet, with a leg 8 feet wide and 6 feet deep attached along part of the 12 foot side. The cut is the line where the leg meets the main area. The main rectangle already includes the corner. The leg is only the part that sticks out.

• Main area: 12 × 10 = 120 sq ft.
• Leg: 8 × 6 = 48 sq ft.
• Floor to cover: 120 + 48 = 168 sq ft.

168 square feet is the floor. It is the number to write on the sketch before you choose a waste percent.

The mistake is to measure the leg through the main area. An 8 foot width times the full 16 foot depth (the 10 plus the 6) is 128 square feet. Added to the 120, that is 248, because the 8 by 10 corner was in both pieces. 248 − 80 = 168. The 80 is the corner you counted twice.

Check the total against the missing notch

The outer box around this L is 12 feet by 16 feet (the 10 plus the 6). That box is 12 × 16 = 192 square feet, and it includes a notch you will not floor. The notch is the part of the 12 foot side the leg does not cover: (12 − 8) × 6 = 24 square feet. 192 − 24 = 168. If the two-rectangle sum and the notch check disagree, one of the edges on the sketch is wrong. Fix the sketch before you order.

The bounding box alone is not the order. 192 square feet charges you for the empty notch.

Enter each rectangle with the room count at 1

The flooring calculator multiplies one length by one width by the number of rooms. That room count is for spaces that really share those dimensions, such as two identical bedrooms. The two legs of an L do not share dimensions.

Run it twice. First run: length 12, width 10, rooms 1. Second run: length 8, width 6, rooms 1. Add the two results. Setting rooms to 2 on the 12 by 10 leg makes 12 × 10 × 2 = 240 square feet and never sees the 48 square foot leg. Averaging the widths, or typing one made-up pair that you hope is “about the L,” is how the 168 slips.

Do the same addition on paper even if you only wanted the square feet. The calculator is there so each rectangle uses the same length and width fields you measured. It is not an L-shaped form.

Waste and boxes are the next page

This measurement stops at 168 square feet. The waste percent, and the step that turns square feet into whole boxes from the coverage printed on the carton, are on the flooring waste guide linked above. That guide already tells you to run mixed rectangles once each and add. Follow it after the sketch totals 168.

What the 168 square feet leaves out

A closet, a doorway landing, or a third jog is another rectangle. Add it the same way, or it is not in the 168. Stairs are not a floor rectangle. Underlayment, reducer strips, and baseboards are separate from the square feet. Measure them on their own once the floor area is settled.