PCB Impedance Calculator

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Microstrip traces run on the outer copper layer over a dielectric. Stripline traces are buried between two ground planes. Edge-coupled types compute differential pair impedance.
All dimension inputs use this unit. Impedance is always in ohms.
Selecting a preset fills the dielectric constant field automatically.
Relative permittivity of the PCB substrate between the trace and the nearest ground plane. FR-4 is typically 4.3-4.7 at 1 GHz.
Width of the copper trace in the selected dimension unit.
mil
1 oz copper = 1.37 mil (34.8 µm). 0.5 oz = 0.7 mil. 2 oz = 2.74 mil. Enter in the selected unit.
mil
Height of the dielectric layer between the trace and the nearest reference plane. Also called substrate height or prepreg thickness.
mil
Optional: enter the trace length to compute total propagation delay, capacitance, and inductance for the full trace.
mil
Characteristic impedance (Z0)Controlled impedance
63.8ohm

Single-ended characteristic impedance of the trace

Effective dielectric constant (Ereff)3.25
Propagation delay6.01ps/mm
Capacitance0.094pF/mm
Inductance0.384nH/mm
Total trace delay7.6ps
63.8 ohm
Low Z0<4050 ohm target40-60Moderate60-80High80-105Very high105+

Z0 = 63.8 ohm

  • Characteristic impedance Z0 = 63.8 ohm. Most RF and high-speed digital traces target 50 ohm.
  • Signal propagation delay is 6.01 ps/mm. A 100 mm trace will delay your signal by about 601 ps.
  • Tolerance on controlled-impedance traces is typically +/-10% (standard) or +/-5% (precision). Coordinate with your PCB fab for layer stack-up details.

Next stepAdjust the trace width or dielectric height to shift Z0 toward your target. Wider traces lower impedance; thicker dielectrics raise it.

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