Estimate feeder current from connected load, demand factor, voltage, power factor, and phase.
This feeder current calculator is intended for planning and load checks. Final feeder design should also consider installation method, conductor temperature rating, harmonics, continuous loading rules, and applicable codes.
Feeder design usually starts with connected load, but feeders are not always sized from connected load alone. In many designs, a demand factor is applied first to represent expected simultaneous use, and then the resulting demand load is converted into current at the selected voltage and power factor. That current becomes the working value for checking conductor size, breaker size, voltage drop, and spare capacity.
This feeder current calculator does that sequence in one step. It takes the connected load in kilowatts, applies a demand factor, converts the demand load to current, and then shows a higher design current using a margin value. That makes the page useful for panels, subpanels, workshop feeders, commercial boards, and preliminary building services calculations.
It is especially useful when the designer already knows the likely connected kW but wants a more realistic feeder current than a simple full connected load assumption.
| Input | Meaning | Unit |
|---|---|---|
| Connected Load | Total real load before diversity or demand is applied | kW |
| Demand Factor | Expected simultaneous use of the connected load | % |
| Power Factor | Real power compared with apparent power | 0 to 1 |
| Voltage | System voltage used for the feeder calculation | V |
| Design Margin | Extra planning allowance above the demand current | % |
Load is entered in kilowatts and the result is shown in amperes. The page reports both the calculated feeder current and the design current after the selected margin. That second value is helpful when users want a more conservative number for early cable and breaker selection.
Connected load = 96 kW, demand factor = 80%, voltage = 400 V, power factor = 0.9, three phase
Demand load = 96 x 0.8 = 76.8 kW
Feeder current = 76,800 / (1.732 x 400 x 0.9) = 123.17 A
With a 125% margin, design current becomes 153.96 A
Connected load = 18 kW, demand factor = 70%, voltage = 230 V, power factor = 0.95
Demand load = 12.6 kW
Feeder current = 12,600 / (230 x 0.95) = 57.67 A
A design margin then pushes the planning current higher for cable and breaker review.
A feeder current result is not the same thing as a final cable size or final breaker size, but it is one of the most useful intermediate values in the design process. Once the current is known, the designer can move into wire size, breaker size, and voltage-drop checks with far more confidence.
This page is intentionally practical: it starts with the demand load idea that many real panels and feeders are based on, then converts the result into current in a clear way. It works well as a first-pass engineering tool before a more detailed code-based load schedule is completed.