Wiring and Protection
Continuous Load Capacity Calculator
Continuous Load Capacity provides a checkable estimate of minimum circuit rating. It is intended for scenario comparison, not as automatic approval of a component or installation.
Set up the Continuous Load Capacity case
Keep every entry on the units shown below.
Input notes
Record ambient temperature, bundling, insulation class, and termination conditions. Nameplate and meter values are not interchangeable unless they describe the same condition.
Values used below a division bar must stay positive. A prefix error can move the result by several orders of magnitude. The next worksheet may be LED Strip Power Supply Calculator if minimum supply rating is needed.
- Continuous load
- Default example: 20 A. Enter continuous load in A.
- Maximum loading
- Default example: 80%. Enter maximum loading in %.
Before accepting the number
Mixing nominal and measured data is a common source of error.
Verify sign, scale, and physical meaning before accepting the number.
Formula used on this page
The displayed result follows rating = load ÷ loading fraction. The entered quantities are Continuous load and Maximum loading.
The defaults produce 25.00 A. Replace them with measurements from one operating state.
Calculate minimum circuit rating from continuous load and maximum loading. Pair this page with Breaker Load Margin Calculator when reviewing unused breaker capacity.
Interpreting the answer
Interpret Minimum circuit rating on the same basis used for the source values. Compare it with the selected conductor and protective-device ratings.
Save the raw entries before testing another scenario. For the companion minimum fuse current calculation, open Electrical Fuse Rating Calculator.
Compare two operating cases
Change Continuous load from 20 A to 24 A while preserving the other measurements. The output changes from 25.00 A to 30.00 A.
Use a separate scenario when multiple conditions change together.
Assumptions and limitations
Use the continuous-load rule required by the governing code.
The arithmetic intentionally leaves out code rules, manufacturer instructions, and field installation details. Use measurements, manufacturer data, or another calculation for effects that can change the decision.
Use the installed route length, conductor material, and actual current path. The broader analysis may also use Dimmer Load Calculator.
Before relying on the answer
How should I prepare the Continuous Load Capacity inputs?
Measured and rated values can represent different states. Use the installed route length, conductor material, and actual current path.
What assumptions affect Minimum circuit rating?
Use the continuous-load rule required by the governing code. Also consider code rules, manufacturer instructions, and field installation details.
Why does the field result disagree with this page?
First confirm that the measurements match the equation. Then review code rules, manufacturer instructions, and field installation details.
Can I change several inputs at once?
Use separate labeled cases when more than one condition changes. Use the installed route length, conductor material, and actual current path.
Does Continuous Load Capacity Calculator choose a final rating?
Use the number as one check, then review the selected conductor and protective-device ratings.