Microstrip Line Calculator

Microstrip Line Calculator. A microstrip line is a flat copper trace on a PCB that carries high-frequency signals — and its width must be precisely calculated to achieve the correct impedance. Enter your target impedance, relative dielectric constant, dielectric thickness, trace thickness, and frequency into the Microstrip Line Calculator to get the required trace width. Secondary outputs include characteristic impedance, effective dielectric constant, and the physical length for a 90° electrical length at your chosen frequency. Also try the calculate Coplanar Waveguide.

Target Impedance (Z₀) *

Desired characteristic impedance of the microstrip line

Relative Dielectric Constant (εᵣ) *

Relative permittivity of the substrate material

Dielectric Thickness (h) *

Thickness of the dielectric substrate

Trace Thickness (t) *

Thickness of the copper trace

Frequency *

MHz

Operating frequency for electrical length calculations

Length Units *

Results

Trace Width (W)

Characteristic Impedance

Effective Dielectric Constant (εₑff)

Electrical Length (90°)

What is a microstrip transmission line?

A microstrip transmission line is a type of electrical transmission line consisting of a conducting strip separated from a ground plane by a dielectric layer. It's commonly used in PCB design for high-frequency applications. See also our calculate Differential Impedance, Odd-Mode Impedance & Even-Mode Impedance — Differential Microstrip.

How do I choose the right characteristic impedance?

Common characteristic impedances are 50Ω for general RF applications, 75Ω for video applications, and 100Ω for differential pairs. Choose based on your system requirements and component specifications.

What materials have typical dielectric constants?

FR-4 PCB material typically has εᵣ = 4.2-4.8, Rogers RO4003 has εᵣ = 3.38, and PTFE has εᵣ = 2.1. Check your substrate manufacturer's datasheet for exact values.

Why is trace thickness important in the calculation?

Trace thickness affects the electric field distribution and thus the characteristic impedance. Thicker traces generally result in lower impedance for the same width.

What is the effective dielectric constant?

The effective dielectric constant (εₑff) accounts for the fact that the electric field in a microstrip is partly in air and partly in the dielectric. It's always between 1 and εᵣ.

How accurate are microstrip calculators?

Modern microstrip calculators using advanced formulas are typically accurate within 1-3% for most practical geometries. For critical applications, consider electromagnetic simulation or measurement verification.

What frequency range is valid for microstrip calculations?

Microstrip formulas are generally valid from DC up to frequencies where the substrate thickness becomes a significant fraction of a wavelength, typically up to several GHz depending on geometry.

How do I convert between mils and millimeters?

1 mil = 0.0254 mm, so multiply mils by 0.0254 to get millimeters, or multiply millimeters by 39.37 to get mils. Our calculator handles unit conversion automatically. You might also find our PCB Trace Width Calculator useful.