PCB Impedance Calculator
Calculate characteristic impedance for microstrip and stripline PCB transmission lines
Calculate PCB Impedance
Width of the copper trace
Thickness of the copper trace (typically 0.5-2.8 mils)
Distance from trace to ground plane
Relative permittivity of substrate material (FR4 ≈ 4.3-4.5)
Impedance Results
Configuration: Microstrip -0.0 × 0.0 mils trace, 0.0 mils substrate
W/H Ratio: NaN - Substrate: εᵣ = 4.5
Impedance Analysis
Example Calculation
50Ω Microstrip Design
Target: 50Ω characteristic impedance
Substrate: FR4 (εᵣ = 4.3), H = 8 mils
Trace: 1 oz copper (T = 1.4 mils)
Required width: ~14.7 mils
100Ω Differential Pair
Target: 100Ω differential impedance
Single-ended: ~50Ω each trace
Coupling: Tight coupling reduces differential impedance
Common: USB, Ethernet, LVDS applications
Common Substrate Materials
Standard Impedances
50Ω
RF, microwave, high-speed digital
75Ω
Video, cable TV, antenna systems
100Ω
Differential pairs (USB, Ethernet)
Design Tips
Wider traces = lower impedance
Thicker substrate = higher impedance
Lower εᵣ = higher impedance
Use controlled impedance for high-speed signals
Consider manufacturing tolerances (±10%)
Understanding PCB Impedance
What is Characteristic Impedance?
Characteristic impedance is the impedance that a transmission line presents to a signal as it propagates along the line. It depends on the physical geometry and materials of the PCB trace and its surrounding dielectric.
Why Control Impedance?
- •Minimize signal reflections
- •Maintain signal integrity
- •Reduce electromagnetic interference
- •Enable high-speed digital communication
Microstrip vs Stripline
Microstrip
Surface trace with ground plane below. More affected by environmental factors but easier to route and modify.
Stripline
Embedded trace between ground planes. Better shielding and more stable impedance but requires more PCB layers.
Note: Calculations are based on IPC-2141A standards and are approximations. Always verify with electromagnetic field solvers for critical applications.