Electrical reference chart
Breaker Size Chart
Use this breaker size chart after the calculator result to document the load category, conductor protection path, standard-size choice, and equipment constraints before selecting an OCPD for the panel schedule.
Quick reference table
Breaker sizing is an overcurrent protection worksheet, not a simple ampere conversion. Use the calculator result with calculated load and load category, then compare conductor ampacity, continuous-load treatment, equipment listing, available fault current, and standard OCPD options before verifying the adopted NEC edition and AHJ requirements.
Breaker size planning paths
| Load category | Record first | What the calculator result must still prove |
|---|---|---|
| General branch circuit | Calculated non-continuous and continuous load portions | Breaker rating coordinates with conductor ampacity and terminal limits |
| Continuous equipment load | Load current and expected operating duration | Planning current and conductor size are both documented |
| Motor load | Table FLC, nameplate FLA, starting method, and overload device | Branch-circuit protection is not confused with overload protection |
| Transformer load | Primary and secondary current, kVA, impedance, and inrush | Equipment-specific primary and secondary protection are reviewed |
| EV charging load | EVSE current setting, circuit rating, service capacity | Long-duration load and panel/service capacity are checked together |
Breaker result risk checks
| Risk check | Why it matters | What to document |
|---|---|---|
| Interrupting rating | Breaker must be suitable for available fault current | Panel rating, series rating data, or study note |
| Conductor protection | Breaker normally protects connected conductors | Selected conductor size, terminal basis, and ampacity screen |
| Equipment listing | Listed equipment can require a maximum or specific OCPD | Nameplate or manual instruction used |
| Standard size step | Next standard size may not always be available for the project path | Reason the selected rating was permitted |
How to use this chart
Classify the load first
Record whether the load is continuous, non-continuous, motor, transformer, HVAC, EVSE, or equipment-specific before choosing a breaker path.
Tie breaker to conductor
Use the breaker calculator result with the wire size or ampacity result so conductor protection, terminal rating, and OCPD selection stay aligned.
Check equipment constraints
Before selecting the breaker, review panel compatibility, interrupting rating, listed equipment maximum OCPD, and manufacturer instructions.
Formula basis
Breaker planning screen = calculated load current adjusted for the load category, then compared with conductor protection limits and permitted standard OCPD sizes.
- Calculated load current is the amperes from the load calculation, nameplate, or calculator result.
- Load category identifies whether the circuit is continuous, non-continuous, motor, transformer, HVAC, EVSE, or equipment-specific.
- OCPD means overcurrent protective device, such as a breaker or fuse selected under the applicable project path.
Worked examples
Continuous 32 A equipment load
The worksheet should show the 32 A load, the planning current used for continuous operation, the conductor ampacity result, and the selected breaker rating before the circuit is released.
Motor feeder review
A motor branch circuit may use one current value for conductor and short-circuit protection while overloads use nameplate data, so the chart keeps both decisions from being collapsed into one breaker number.
Related calculators
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Related charts
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EV Charger Wire Size Chart
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Frequently asked questions
These answers explain how to use the chart without turning a quick reference into a final design decision.