To find the area of an L-shaped room, split it into two rectangles, find the area of each and add them together. A room that is 14 ft on its long side, with a 6 × 5 ft corner cut out, measures 14 × 12 − 6 × 5 = 138 sq ft. Either method below gives the same answer; pick whichever needs fewer measurements in your room.
Method 1: split it into rectangles
- Draw a rough sketch of the room. It does not need to be to scale.
- Draw a line that splits the L into two rectangles. Extend one of the inside walls across the room.
- Measure the length and width of each rectangle.
- Multiply length × width for each one.
- Add the results.
For the room above: rectangle A is 8 × 12 = 96 sq ft, rectangle B is 6 × 7 = 42 sq ft. Total: 138 sq ft.
Method 2: measure the big box, subtract the notch
Imagine the room filled out into a full rectangle, then take away the missing corner. For the same room, the outer box is 14 × 12 = 168 sq ft. The missing corner is 6 × 5 = 30 sq ft. 168 − 30 = 138 sq ft, the same as before.
This method is quicker when the notch is small, such as a closet or a chimney chase that juts into the room.
Formulas for other shapes
| Shape | Area | Where you see it |
|---|---|---|
| Rectangle | length × width | Most rooms |
| Right triangle | base × height ÷ 2 | Angled walls, corner nooks |
| Trapezoid | (side a + side b) ÷ 2 × height | Bay windows, angled hallways |
| Circle | 3.1416 × radius² | Round tables, column bases |
| Half circle | 3.1416 × radius² ÷ 2 | Rounded alcoves |
Measuring in feet and inches
Tape measures read in feet and inches, but the math needs decimal feet. Divide the inches by 12 and add them to the feet: 11 ft 6 in is 11 + 6 ÷ 12 = 11.5 ft.
| Inches | 3 | 4 | 6 | 8 | 9 | 10 |
|---|---|---|---|---|---|---|
| Feet | 0.25 | 0.33 | 0.5 | 0.67 | 0.75 | 0.83 |
What to include and what to leave out
- Closets: include them if you are tiling or putting flooring in them.
- Cabinets and islands: leave them out for tile, unless they are coming out.
- Under appliances: include the space under a dishwasher or range, so the appliance can slide out at floor height.
- Doorways: include the floor in the doorway up to the middle of the door, where the transition strip sits.
- Tubs and showers: leave them out of the floor area. Measure tile on the walls around them as a separate area.
Tips for an accurate measurement
- Measure at floor level. Walls are rarely perfectly straight, and baseboard height is where the flooring meets them.
- Measure each wall twice, at both ends. If the numbers differ, use the larger one.
- Round up to the next inch, never down.
- Write every measurement on your sketch as you take it.
Once you have the total, enter it in the tile calculator with the “I know the sq ft” option to get tile and box counts.