Calculator

Breaker sizing per NEC, automatic

Overcurrent protection device sizing that follows NEC 240 automatically. Standard trip sizes from NEC 240.6. Changes to loads flow through to breaker sizes instantly.

What you get

NEC 240 compliant

Overcurrent protection sizing follows NEC 240 requirements including next-standard-size rules.

Standard trip sizes

Sizes selected from NEC 240.6 standard ampere ratings. No non-standard values.

Fault duty checks

Breaker interrupting capacity checked against calculated fault currents automatically.

Coordination awareness

See upstream and downstream device sizes to evaluate coordination.

Live sizing

Change a load and breaker sizes adjust throughout the circuit.

Override when needed

Override any auto-sized breaker when engineering judgment requires it.

OCPD sizing that stays current with your design

Manual breaker sizing means recalculating every time a load changes. ekx keeps every breaker in your system sized correctly, automatically, as your design evolves.

  • Breakers size automatically based on connected load and NEC rules
  • Standard trip sizes selected from NEC 240.6
  • Interrupting capacity checked against fault currents
  • Sizes update live as loads change

Start free. Upgrade when you need more.

Free tier includes 1 project with up to 2 buses. Paid plans start at $27/month for consultants and $149/month for unlimited access.

View All Plans

Frequently asked questions

Which NEC sections does it follow?

NEC 240 for overcurrent protection sizing, including NEC 240.4 for protection of conductors and NEC 240.6 for standard ampere ratings.

Does it check interrupting capacity?

Yes. Breaker interrupting ratings are automatically compared against calculated fault currents at each bus. Underrated devices are flagged.

Can I override the auto-sized values?

Yes. Any breaker size can be overridden manually. The system will flag if your selected size doesn't meet NEC minimums.

Does it work for fuses too?

Yes. The OCPD sizing applies to both breakers and fuses, following the same NEC requirements.

Every breaker sized per NEC, automatically.

OCPD sizing that updates as you design.

Start Free