PCB Trace Width Calculator
Calculate minimum PCB trace width for a given current. Enter circuit values to calculate the selected electrical quantity.
Parameters
Electronics guide · Signals, timing, and radio frequency
About PCB Trace Width Calculator
Estimate an external copper trace width from current, allowed temperature rise, and copper thickness. The output includes width in mils and millimeters and a cross-sectional area based on the calculator's IPC-2221-style approximation.
Signal and RF calculations connect frequency, period, wavelength, bandwidth, sampling, impedance, and ratios. Results often assume ideal propagation or a simplified signal model; real cables, antennas, clocks, and converters can add losses, tolerances, reflections, and environmental effects.
How to Use This Tool
- 1.Enter the current the trace must carry and the allowed temperature rise.
- 2.Select or enter copper thickness in ounces per square foot as shown.
- 3.Calculate the suggested width and compare it with board space, copper weight, and the design standard you are using.
Technical Details to Check
1.Frequency and time are linked
For a periodic signal, period is the reciprocal of frequency. Convert prefixes carefully: hertz, kilohertz, megahertz, and gigahertz differ by powers of one thousand.
2.Propagation depends on the medium
Wavelength is related to frequency and propagation speed. A free-space estimate differs from wavelength in a cable or material where the signal travels more slowly.
3.Logarithmic ratios need a reference
Decibels and related units describe ratios, often with a stated reference such as dBm. Check whether the tool is converting power, voltage, or a normalized ratio before using the value.
4.Sampling is not reconstruction quality
A sampling condition can help assess whether a signal's frequency content is representable, but real filters, clock jitter, noise, and system bandwidth also affect sampled data.
How the Calculation Works
The client applies an IPC-2221 external-trace approximation: cross-sectional area is derived from current and temperature rise using empirical constants, then width is calculated from area and copper thickness. It does not calculate an internal-layer trace; those have different heat-transfer assumptions.
Worked Example
A higher current or lower permitted temperature rise generally requires a wider trace under the same copper thickness.
Where This Tool Can Help
Make an early routing estimate for a simple external PCB trace and compare the effect of copper weight or temperature-rise assumptions.
Converting signal units
Move between frequency, time, wavelength, or power representations while keeping the source unit and reference clear.
Checking a communications setup
Estimate baud timing, clock tolerance, or signal ratios, then compare the result with the transceiver and protocol requirements.
Planning an RF or antenna estimate
Use a frequency-based result as a starting point and account separately for material, antenna geometry, matching, and the surrounding environment.
Reviewing sampled signals
Check a theoretical sampling relationship before testing the actual signal path, filters, converter limits, and clock quality.
Tips for More Reliable Results
- Write down the frequency, time, impedance, and reference units before entering a value.
- Check whether the formula assumes free-space propagation, ideal components, or a matched load.
- For dB values, identify the reference and whether the underlying quantity is power or amplitude.
- Compare theoretical results with datasheets, measured behavior, and the operating frequency range.
Limitations and Assumptions
Trace heating also depends on ambient temperature, board stackup, nearby copper, airflow, length, vias, and manufacturing quality. Standards and calculators use different assumptions. Treat the answer as guidance for review, not a safety certification; validate with a recognized design tool and applicable requirements.
Signal calculations describe a model, not a complete measurement of a physical system. Propagation medium, component tolerance, noise, impedance mismatch, bandwidth, and instrument limitations may not be represented by the inputs.
Frequently Asked Questions
Does this apply to inner-layer traces?
No. The current page uses an external-trace approximation.
What is a mil?
It is one thousandth of an inch; the page also reports millimeters.
Does the result guarantee a safe temperature?
No. Real thermal conditions and design rules must be evaluated.
Is wavelength always the free-space value?
No. The medium changes propagation speed, so a cable or material can have a shorter wavelength than free space.
Does a sampling calculation guarantee a clean digital signal?
No. Filtering, noise, clock accuracy, converter performance, and signal bandwidth also matter.