CALCULATORS / PCB INTERCONNECT AND PACKAGING

PCB trace resistance calculator

Uniform rectangular copper conductor; temperature rise omitted.

pcb-trace-resistance.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	resistanceohm	dropmV	lossW
	0.048	48	0.048
	0.0384	38.4	0.0384

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

voltage drop budget48.00 mV✓ passes

BASELINE INPUTS

resistivity1.68e-8 ohm*mlength100 mmwidth1 mmthickness35 umcurrent1 A

CALCULATED

resistance0.048 ohm

drop48 mV

loss0.048 W

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# PCB trace resistance
# Scope: Uniform rectangular copper conductor; temperature rise omitted.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

resistivity = 0.0000000168 ohm*m
length = 100 mm
width = 1 mm
thickness = 35 um
current = 1 A

resistance := resistivity*length/(width*thickness) [ohm]
drop := current*resistance [mV]
loss := current^2*resistance [W]

check voltage drop budget: drop <= 100 mV

scenario alternative: resistivity = 1.344e-08 ohm*m

Calculated from your source · not saved

Baseline · Baseline

voltage drop budget48.00 mV ✓ passes

alternative · alternative

voltage drop budget38.40 mV ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

resistance: resistance = resistivity*length/(width*thickness) [ohm]
drop: drop = current*resistance [mV]
loss: loss = current^2*resistance [W]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

resistivity: 1.68e-8 ohm*m
length: 100 mm
width: 1 mm
thickness: 35 um
current: 1 A

Calculated

resistance: 0.048 ohm
drop: 48 mV
loss: 0.048 W

Assumptions and limits

Uniform rectangular copper conductor; temperature rise omitted.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: PCB trace resistance. Inputs: length; width; copper thickness; temperature. Outputs: resistance; voltage drop; resistive loss. Model scope: Explicit stackup and trace/via geometry; empirical models identified. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: length, width, copper thickness, temperature
Outputs: resistance, voltage drop, resistive loss
Modes: calculate, compare, sweep
Drawing: Layer viewer and cross section

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS