Microstrip Line Calculator
Estimate the characteristic impedance of a PCB microstrip trace, or find an initial trace width for a target impedance. A microstrip has a signal trace above a ground plane, separated by a dielectric substrate.
Use the units printed beside each field. On a small screen, scroll the calculator horizontally to see all inputs and results.
Inputs and units
- er
- Relative permittivity of the substrate; dimensionless.
- h (mm)
- Dielectric height between the signal trace and the ground plane.
- t (µm)
- Copper thickness. Enter micrometres here, not millimetres.
- f (MHz)
- Operating frequency in megahertz.
- W (mm)
- Signal trace width used by Analyze.
- Zo (Ω)
- Target characteristic impedance used by Synthesis.
How to use this calculator
For the built-in example, er = 4.5, h = 1 mm, t = 18 µm, f = 1000 MHz and W = 1.85192 mm give approximately 50 Ω. These are example values, not a recommended PCB stackup.
Reading the results
Read impedance in ohms and synthesized dimensions in millimetres. Effective permittivity and velocity factor describe the propagation estimate; the quarter-wavelength output is in millimetres.
Before using the result in a design
Use the PCB manufacturer’s actual dielectric height and material data. Solder mask, material tolerances, copper profile and nearby conductors can change the final impedance. Confirm production designs with your PCB manufacturer or an appropriate field solver.
Blank fields use the tool’s built-in example defaults; always enter and check your actual design values.
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