Microstrip / Stripline / Differential Pair
Calculate characteristic impedance for high-speed PCB traces using our free online impedance calculator. Supports microstrip, stripline, and differential pair configurations for USB, HDMI, PCIe, DDR, and other high-speed interfaces.
Calculate microstrip impedance using Hammerstad-Jensen equations. Ideal for surface layer routing where traces run above a ground plane with controlled dielectric height.
Calculate stripline impedance for traces sandwiched between two ground planes. Provides better EMI shielding and consistent impedance for sensitive high-speed signals.
Calculate differential pair impedance for USB, HDMI, LVDS, and other high-speed interfaces. Design 90Ω, 100Ω, or custom differential impedances with edge or broadside coupling.
Impedance mismatches cause signal reflections that degrade eye diagrams and increase bit error rates. Proper impedance control ensures clean signal transmission for high-speed digital interfaces.
Controlled characteristic impedance reduces electromagnetic emissions and improves immunity. Essential for meeting FCC, CE, and other regulatory requirements.
USB 2.0/3.0 (90Ω), HDMI (100Ω), PCIe (85Ω), DDR4 (40-60Ω) all require precise impedance matching. Our calculator supports all common interface standards.
Use our impedance calculator to optimize your PCB stackup before fabrication. Adjust trace width, dielectric thickness, or copper weight to achieve target impedance.
Specify your target impedance (50Ω, 100Ω, etc.) and automatically calculate the required trace width for your stackup parameters.
Supports FR-4, Rogers, Isola, Megtron, and custom dielectric constants. Accurate impedance calculation for standard and high-frequency materials.
Characteristic impedance (Z₀) is the ratio of voltage to current for an electromagnetic wave propagating along a transmission line. For PCB traces, this impedance depends on trace geometry, dielectric properties, and the relationship to reference planes.
Our microstrip impedance calculator uses the Hammerstad-Jensen equations, which are accurate within ±2% for typical PCB geometries. For stripline impedance, we use IPC-2141 formulas optimized for symmetric stripline configurations.
Differential pair impedance depends on both the single-ended impedance of each trace and the coupling between traces. Tighter coupling (smaller spacing) increases coupling factor and typically reduces differential impedance. Our calculator handles both edge-coupled and broadside-coupled configurations.
For production PCBs, always specify impedance control to your fabricator and expect ±10% tolerance for standard processes. Critical applications may require test coupons and TDR (Time Domain Reflectometry) verification to ensure impedance accuracy.
Characteristic impedance (Z₀) is the ratio of voltage to current for a wave traveling along a transmission line. For high-speed signals, impedance mismatches cause reflections that degrade signal integrity. Standard impedances are 50Ω for single-ended and 100Ω for differential signals in most applications.
Microstrip (surface trace over ground plane) is easier to manufacture and preferred for most high-speed signals. Stripline (trace between two ground planes) provides better shielding and consistent impedance but is more expensive. Use stripline for sensitive signals requiring EMI protection or when routing through inner layers.
These formulas (Hammerstad-Jensen for microstrip, IPC-2141 for stripline) are accurate within ±5% for typical PCB geometries. For production, always specify impedance control to your fab house and expect ±10% tolerance. Critical applications may require test coupons and TDR verification.
Standard FR-4 has Er = 4.2-4.8, typically 4.5 at 1MHz. For high-speed designs (>1GHz), use frequency-dependent values from your laminate datasheet. Low-loss materials like Rogers (Er ≈ 3.5) or Megtron (Er ≈ 3.4) are preferred for multi-gigabit signals.
Start with single-ended traces at ~50-55Ω, then adjust spacing for 100Ω differential. Tighter coupling (smaller spacing) increases coupling and reduces differential impedance. Common configurations: USB 3.0 (90Ω), HDMI (100Ω), PCIe (85Ω). Always verify with your fab's stackup.
Yes, thicker copper (higher oz weight) slightly reduces impedance due to the increased cross-sectional area. The effect is typically 1-3Ω for standard copper weights. Our calculator accounts for copper thickness in impedance calculations.
High-Speed Design•14 min Microstrip vs Stripline vs CPW Guide Compare microstrip, stripline, and coplanar waveguide for high-speed PCB design. Impedance calculations and use cases.
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Our impedance calculator is part of a comprehensive PCB design toolkit. Calculate trace widths for power delivery or analyze via current capacity for layer transitions.
