Calculators / 09
PCB Channel Loss Budget Calculator
A PCB trace loses signal two ways: in the copper, where skin effect and roughness raise the resistance, and in the laminate, where the field does work on the dielectric. The copper term grows as √f and the dielectric term as f, so at high enough frequency the laminate always wins — and which one dominates your channel decides whether a wider trace or a better laminate is the fix.
Reading the numbers
- The dielectric loss is 2.3·f·Df·√Dk dB per inch with f in GHz: halving Df halves it.
- A wider trace lowers only the conductor term. It is a real fix only while the conductor term is the larger one.
- The margin is the budget minus the loss; a negative margin means the channel needs a better laminate, smoother copper, a shorter run or more equalisation.
Every value is in the address bar as you change it, so a link reproduces the calculation exactly.
Type values with SI prefixes — 100n, 2.2p, 16G — or
drag the sliders; a bare number keeps the prefix already shown.
The formulas
Go deeper — assumptions, how it is checked, and sources
Assumptions. The conductor term is first-order: it puts the current on one face of the strip and treats the return path as lossless. In stripline the current splits across both faces, which halves the strip's resistance, while the planes add some back; the combination lands within roughly ±30% of a field solve. Dk and Df are taken as constant with frequency, and roughness uses the Hammerstad–Bekkadal multiplier on the RMS roughness.
How it is checked. Zero Df gives zero dielectric loss; dielectric loss is linear in f and in length; smooth-copper conductor loss is exactly √f; and the conductor term agrees with the published rule of thumb 36·√f / (w·Z0) dB/in to within 5%.
Sources. D. M. Pozar, Microwave Engineering, 4th ed., Wiley, 2012, §2.7; E. Bogatin, Signal and Power Integrity — Simplified, 3rd ed., Pearson, 2018, ch. 9.