USB Trace Width Calculator
USB 2.0 | USB 3.0/3.1/3.2 | USB 4.0
Calculate trace width and differential impedance for USB high-speed designs. From USB 2.0 at 480 Mbps to USB 4.0 at 80 Gbps, get the right 90Ω differential pair dimensions for reliable signal integrity.
USB Impedance Requirements
| USB Version | Max Speed | Differential Impedance | Signaling |
|---|---|---|---|
| USB 2.0 | 480 Mbps | 90Ω ±10% | Differential |
| USB 3.0/3.1 | 5/10 Gbps | 90Ω ±10% | Differential |
| USB 3.2 | 20 Gbps | 85-90Ω | Differential |
| USB 4.0 | 40/80 Gbps | 85Ω ±10% | Differential |
USB PCB Design Guidelines
90Ω Differential
USB requires 90Ω differential impedance (45Ω single-ended per trace). Use our impedance calculator to determine exact trace width and spacing for your stackup.
Length Matching
Keep D+ and D- traces within 5 mils (0.127mm) of each other. For USB 3.0+, match TX and RX pairs separately with tighter tolerances.
Reference Planes
Route USB signals over continuous ground planes. Avoid splits or gaps that could cause impedance discontinuities and signal reflections.
Typical USB Trace Dimensions
4-Layer Board (1.6mm, FR4)
6-Layer Board (1.6mm, FR4)
* These are typical values. Use our calculator with your actual stackup for accurate results.
USB Version Design Considerations
USB 2.0 High-Speed
- • 90Ω differential impedance
- • Single differential pair (D+/D-)
- • Relaxed routing constraints
- • Max trace length ~6 inches
- • Standard FR4 is sufficient
USB 3.0+ SuperSpeed
- • 90Ω differential for each pair
- • Multiple differential pairs (TX/RX)
- • Tighter length matching required
- • Loss budget considerations
- • Consider low-loss materials for long runs
Calculate Your USB Trace Dimensions
Use our free impedance calculator to determine exact trace width and spacing for your USB design. Enter your stackup parameters for accurate 90Ω differential calculations.
USB Design FAQ
What impedance do I need for USB?
USB requires 90Ω differential impedance (±10% tolerance). This is 45Ω per trace (single-ended) with the traces coupled together.
What's the max USB trace length?
USB 2.0 allows ~6 inches on PCB. USB 3.0+ has loss budgets rather than length limits—typically 4-8 inches depending on material and frequency.
Do I need controlled impedance for USB 2.0?
Technically yes, but USB 2.0 is forgiving. USB 3.0 and higher absolutely require controlled impedance with tighter tolerances.
How tight should length matching be?
USB 2.0: within 150 mils. USB 3.0: within 5 mils per pair. USB 4.0: even tighter, consult specification.
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