Propagation Delay Calculator
Calculate signal propagation delay in PCB traces. Enter circuit values to calculate the selected electrical quantity.
Trace Parameters
Electronics guide · Signals, timing, and radio frequency
About PCB Propagation Delay Calculator
Estimate signal travel delay along a PCB trace from its length, dielectric constant, and whether the trace is modeled as microstrip or stripline. The result includes total delay, delay per inch, and a calculated velocity estimate.
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.Choose microstrip on the surface or stripline within an internal layer.
- 2.Enter dielectric constant and trace length in inches as labeled.
- 3.Calculate and review the estimate. Use actual stackup dimensions and dielectric data for a design decision.
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 page uses different approximate delay-per-inch expressions for microstrip and stripline based on relative dielectric constant, then multiplies by trace length. A higher effective dielectric constant generally slows signal propagation. The structure and formula are simplified representations of transmission-line behavior.
Worked Example
If a modeled route has 100 ps/in delay and is 4 inches long, the ideal total estimate is about 400 ps before routing and material variation.
Where This Tool Can Help
Estimate timing skew or signal travel time across a board route and compare approximate trace lengths.
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
Real propagation depends on stackup geometry, field distribution, frequency, material dispersion, copper, and discontinuities. The tool's labels do not replace a field solver or measurement. For high-speed timing closure, use the fabricator's data and signal-integrity analysis.
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 a longer trace add delay?
Yes. Under the same propagation model, total delay scales with length.
Why are microstrip and stripline different?
Their electromagnetic fields occupy different proportions of air and dielectric.
Can I use this for final high-speed timing?
Use it for a rough estimate only; validate with stackup-specific tools and measurements.
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.