PCB Impedance Calculator
Calculate trace impedance or required width for controlled impedance PCB designs. Supports microstrip, stripline, coplanar waveguide, and differential pairs.
Single-ended trace on outer layer
Standard FR-4 laminate for general purpose applications
Formula Reference
Microstrip: Z₀ = (87 / √(εr + 1.41)) × ln(5.98H / (0.8W + T))
Based on IPC-2141 approximations. Results should be verified with field solver for critical applications.
Industry-Standard Formulas
Based on IPC-2141 equations for accurate impedance calculations verified against professional tools.
5 Trace Structures
Supports microstrip, stripline, coplanar waveguide, and edge-coupled differential pairs.
Export & Quote
Download calculation results as PDF or request a quote with pre-filled impedance specifications.
Frequently Asked Questions
What is controlled impedance?
Controlled impedance refers to PCB traces designed to have a specific characteristic impedance, typically 50Ω for single-ended signals or 90-100Ω for differential pairs. This is critical for high-speed digital and RF designs to minimize signal reflections.
When should I use microstrip vs stripline?
Microstrip is used for outer layer traces and is easier to manufacture and probe. Stripline provides better EMI shielding and is preferred for sensitive signals on inner layers. Stripline also has more consistent impedance but requires more board layers.
How accurate are these calculations?
These calculations use IPC-2141 approximations which are typically accurate within 5% for standard PCB geometries. For critical applications, we recommend verification with a 2D/3D field solver or requesting a controlled impedance test coupon with your order.
What dielectric constant should I use for FR-4?
Standard FR-4 has εr ≈ 4.3 at 1MHz, but this varies with frequency and manufacturer. For high-frequency designs, consider using low-loss materials like Rogers 4350B (εr ≈ 3.48) which have more stable dielectric properties.