In short
Split the room into rectangles and triangles, work out each part and add them up. A five-sided room of 14 × 10 ft with a point of 4 ft on one side is 140 + 28 = 168 sq ft. Easier: type the corners below, or draw the room in the editor.
Split it into shapes you know
Look for the biggest rectangle that fits, then deal with what is left: triangles for slanted walls, smaller rectangles for nooks. Work out each part and add them up.
The example, part by part
| Part | Size | Area |
|---|---|---|
| Rectangle | 14 × 10 ft | 140 sq ft |
| Triangle on top | base 14 ft, height 4 ft | 28 sq ft |
| The whole room | five corners | 168 sq ft |
Three ways to get the area
- Split into rectangles and triangles: good for one slanted wall or one nook.
- Type the corners: measure how far each corner is from one wall and from the wall next to it, and the calculator adds it all up.
- Draw it: in the editor you click the corners, and every area is there while you draw. No formula to choose, and no adding to get wrong.
Measure the corners
- Pick two walls that meet at a right angle, for example the left wall and the top wall. They are your zero lines.
- For every corner, measure the distance to the left wall and the distance to the top wall.
- Type the corners in the order you walk around the room. The order matters: the sides may not cross.
- Check the result against a simple rectangle around the room: the area must be smaller.
Why drawing beats formulas
A room with three slanted walls needs several triangles and a lot of care. In the editor you draw the walls the way they are, and the room measures itself, with the same calculation as this page. Draw this room opens the room above to show how it works.
Figure 1. One floor of 25 × 17 ft. The rooms add up to 425 sq ft.
About this page · Written by the Squaremetry team. Last checked on October 1, 2026. Found a mistake? Send us a message.