Calculator Inputs
The page stays single-column overall, while the calculator fields switch to three, two, or one columns by screen size.
Example Data Table
Use these sample cases to test the calculator or explain results to clients, students, or team members.
| Scenario | System | Voltage | Input | Demand | Continuous Factor | Required Ampacity | Breaker |
|---|---|---|---|---|---|---|---|
| Lighting Feeder | Single Phase | 230 | 4200 W | 100% | 125% | 26.44 A | 30 A |
| Workshop Circuit | Single Phase | 230 | 32 A | 90% | 125% | 39.60 A | 40 A |
| HVAC Panel | Three Phase | 400 | 18000 W | 100% | 125% | 38.03 A | 40 A |
| Battery Cabinet | DC | 48 | 2200 W | 100% | 125% | 61.44 A | 70 A |
| Mixed Equipment | Three Phase | 415 | 25000 W | 85% | 125% | 49.88 A | 50 A |
Formula Used
This calculator follows common continuous-load style sizing logic for planning. Always verify exact requirements under your local code and equipment documentation.
How to Use This Calculator
- Enter a circuit label so exported files stay easy to identify.
- Choose whether you are starting from connected power or measured current.
- Select the system type: single phase, three phase, or DC.
- Fill in voltage and the load value for your chosen mode.
- For AC systems, enter power factor. Then set efficiency, demand factor, and continuous factor.
- Add safety margin and any ambient or bundling derating factors.
- Click the calculate button to show results above the form.
- Review the graph, summary cards, and export CSV or PDF reports if needed.
Frequently Asked Questions
1) What is a continuous load?
A continuous load generally operates for three hours or longer. Many design rules size breakers and conductors above the actual running current to manage heat and long-duration stress.
2) Why does the calculator use a continuous factor?
The continuous factor increases the adjusted current to a safer design value. A common planning value is 125%, but exact requirements depend on the electrical code, equipment listing, and installation method.
3) When should I use power mode instead of current mode?
Use power mode when you know watts or kilowatts from equipment data. Use current mode when you already measured amperes or received current directly from another study.
4) Why are demand factor and safety margin separate?
Demand factor reflects expected usage diversity. Safety margin is an extra design cushion chosen by the engineer or planner. Keeping them separate makes assumptions easier to audit and explain.
5) What do ambient and bundling factors do?
They reduce effective conductor carrying capacity when temperature is high or many conductors share the same raceway. Lower factors increase the ampacity required from the conductor selection.
6) Does the breaker recommendation guarantee code compliance?
No. The result is a planning estimate. Final compliance also depends on conductor temperature ratings, terminal limits, installation conditions, overcurrent rules, and the governing electrical standard.
7) Can I use this for three-phase industrial loads?
Yes, the calculator supports three-phase estimation. Still, confirm line voltage conventions, motor starting behavior, harmonics, and equipment-specific protection rules before finalizing a design.
8) Why is breaker headroom useful?
Headroom shows how much usable continuous capacity remains on the suggested breaker after the adjusted load is applied. It helps compare alternatives and identify tight designs early.