calctricFrom input to answer.
- Set the region to Canada and open All Tools → Box Fill.
- Choose a listed box or enter an appropriate marked volume. Add any qualifying ring or extender.
- Enter wires and their roles, devices and depths, connector groups and applicable internal fittings.
- Review the allowance or volume result and any compatibility warning, not just the remaining space.
WORKED EXAMPLE
The app’s single-gang example
Enter
Tap Example: four 14 AWG wires, one receptacle at 25 mm depth and three connectors in the listed 12.5 cu in single-gang box.
Read the result
The app reports 7 of 8 allowances used, with 1 remaining. This is an allowance calculation for that listed setup, not a promise that any similarly sized device will physically fit.
Get more from it.
- A passing conductor, internal-only pigtail and bonding conductor may be treated differently. Select the correct role.
- Device depth matters. A deeper device can change the volume calculation.
- Listed allowance counts and a custom marked-volume calculation are distinct paths; do not interchange them casually.
Know the limits.
- CEC 2024 calculation within the app’s supported scope. Mounting geometry, partitions, wet-location suitability, fan support and fire ratings require separate checks.
Verify the inputs, applicable local requirements and real conditions. The app is a calculation aid and can contain errors. See our terms and safety disclaimer.
Common questions.
Why can a custom-volume box differ from a listed box?
The app preserves the applicable listed allowance method where supported. A marked-volume calculation uses volume rather than simply copying a listed count.