PCB and Transmission Lines
Model class: Exact ideal relationship
PCB trace resistance and voltage drop
Calculate DC trace resistance, voltage drop, and I squared R loss from copper trace geometry and current.
Interactive engine
Start with the stated conditions.
Values stay in this browser. Choose a representative scenario, then calculate deliberately.
Example ready
Calculate to inspect the result.
The result will identify the direct answer, assumptions, and any warning that changes the next decision.
Assumptions to check
- The entered PCB-trace-resistance values represent the stated operating condition.
- This exact ideal relationship is evaluated in the declared lumped or first-pass model.
- A PCB-trace-resistance calculation is not a component qualification or safety approval.
What this PCB-trace-resistance calculation establishes
Calculate DC trace resistance, voltage drop, and I squared R loss from copper trace geometry and current. The useful result is the stated electrical quantity and the decision it supports, not an unstated claim about a finished product. This engine keeps the governing relationship visible so an input, unit, condition, or model boundary can be reviewed before a value becomes a component or layout choice.
Resistance is copper resistivity times length divided by cross-sectional area (width times thickness); voltage drop and I squared R loss follow from the entered current. Treat the number as a first-pass result for the declared operating point. When a source, load, temperature, frequency, waveform, component tolerance, or measurement condition changes, repeat the calculation at the relevant corner rather than assuming the nominal answer persists.
Worked decision context
A copper trace 100 mm long, 1 mm wide, and 35 µm thick at 20°C has about 49.26 mΩ; at 2 A the drop is 98.5 mV. That example verifies the equation and illustrates the scale of the result, but it does not select a part by itself. Compare the result with available values, ratings, tolerance bands, and the receiving circuit or physical environment before implementation.
Use the primary output to identify the binding constraint. If it leaves little margin, document which input dominates and use selected-part data, a higher-fidelity model, simulation, or measurement. This is especially important when a small numerical difference changes a thermal, timing, noise, or reliability decision.
Limits and validation handoff
This is an ideal rectangular DC model at one reference temperature. Copper thickness tolerance, temperature rise, and AC skin effect at high frequency all change the real resistance. The calculation does not silently include omitted parasitics, installation conditions, manufacturing variation, or product policy. Those conditions can be decisive even when the arithmetic is exact for the selected model.
Record inputs, units, model assumptions, and the intended decision with the result. Verify the leading risk against the selected component data sheet and a representative measurement when the circuit has consequential energy, high voltage, safety, compliance, or reliability requirements.
Common mistakes
- Treating the PCB-trace-resistance result as a guaranteed operating limit rather than a first-pass exact ideal relationship estimate.
- Mixing a data-sheet value measured under one condition with this PCB-trace-resistance calculation performed at another.
- Selecting a component before checking the boundary this calculation names: this is an ideal rectangular DC model at one reference temperature. Copper thickness tolerance, temperature rise, and AC skin effect at high frequency all change the real resistance.
Model limit and handoff
Keep the entered PCB-trace-resistance conditions with the calculation, then validate the binding limit using the selected component, physical implementation, and representative operating corner.
FAQs
Is this PCB-trace-resistance result sufficient to approve a design?
No. It applies exact ideal relationship reasoning to the entered PCB-trace-resistance values and names the checks that still need selected-part data, a higher-fidelity model, or measurement. This is an ideal rectangular DC model at one reference temperature. Copper thickness tolerance, temperature rise, and AC skin effect at high frequency all change the real resistance.
What does this PCB-trace-resistance calculator assume that could make the result wrong?
Resistance is copper resistivity times length divided by cross-sectional area (width times thickness); voltage drop and I squared R loss follow from the entered current. If the entered values do not match the real operating condition, the result no longer describes the actual circuit.
Where should this PCB-trace-resistance result go next?
Compare this PCB-trace-resistance result with Limits of PCB current and temperature estimates, then use the stated next decision below the calculator to move from this first-pass number toward an implementation.