What this calculator does

Check whether a basement bedroom window is large enough to climb out of in an emergency, using typical Ontario size rules.

How to use it

1. Measure the clear opening, not the frame: the width and height you can actually pass through with the window fully open.
2. Measure the height of the sill from the floor.
3. Enter the numbers and read whether they pass.

Why it matters

A bedroom needs a way out in a fire. For basement bedroom windows the Ontario Building Code asks for an unobstructed opening of at least 0.35 square metres (about 3.8 sq ft) with no dimension less than 380 mm (15 in), and a sill that is not too high. Many older basements fail this check, and a larger window or a window well is one of the key steps in a legal basement apartment.

Tips from the job site

• Measure with the window fully open. The sash and hardware reduce the clear area.
• A window well needs enough clear space and a way to climb out.
• Final approval is by your city inspector. This tool is a first check only.

These results are estimates. We measure on site before we quote, and we confirm local rules with your city.