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PCB Controlled Impedance & Precise Trace Width Calculator
NextPCB's PCB Impedance Calculator matches your target impedance to NextPCB's actual manufacturable stack-ups. Enter your layer count, board thickness, and copper weight to get a trace width, spacing, and ground separation ready for layout — within NextPCB's standard ±10% tolerance, or a tightened ±5% for critical high-speed links.
Free desktop tool for full stack-up & DFM analysis
How the Impedance Calculator Works
- Set your board parameters. Layer count, board thickness, outer and inner copper weight, and whether blind/buried vias are needed — these define which of NextPCB's manufacturable stack-ups the calculator matches against.
- Enter your target impedance and signal layer. Choose the impedance model for that layer (e.g. single-ended), and optionally specify upper/lower reference planes if your design already fixes them.
- Get manufacturable dimensions. The calculator returns the trace width, trace spacing, and ground separation needed to hit your target on a real NextPCB stack-up — not a theoretical laminate — so results are ready to carry into layout and fabrication.
Standard PCB fabrication holds impedance to within ±10% of target. For high-speed interfaces where signal integrity margin is tight, NextPCB also supports a tightened ±5% tolerance — flag this when you place your order so the fab process is adjusted accordingly.
Quick Reference: Key Terms
- Characteristic Impedance (Z0)
- The impedance a signal "sees" as it travels along a trace, determined by trace geometry and the surrounding dielectric; commonly targeted at 50Ω single-ended or 90–100Ω differential.
- Single-ended Impedance
- The impedance of one trace measured relative to a reference (ground) plane, as opposed to being paired with a second, complementary trace.
- Differential Impedance
- The impedance between two coupled traces carrying equal and opposite signals (a differential pair), used for interfaces such as USB, PCIe, HDMI, and LVDS.
- Microstrip
- A trace routed on an external (top or bottom) layer, referenced to a ground plane below it, with the other side exposed to air or solder mask.
- Stripline
- A trace routed on an internal layer, fully embedded in dielectric between two reference planes above and below it.
- Controlled Impedance Tolerance
- The allowed deviation from a target impedance value during fabrication; NextPCB's standard process is ±10%, with a tightened ±5% option available for high-speed designs.
Frequently Asked Questions
What is controlled impedance and why does it matter?
Controlled impedance means a trace's characteristic impedance (Z0) is held within a specified tolerance of a target value — typically 50Ω single-ended or 90–100Ω differential — by controlling trace width, spacing, dielectric height, and copper weight during fabrication. It matters for high-speed signals because an impedance mismatch causes reflections, which degrade signal integrity and can cause data errors.
What impedance tolerance does NextPCB manufacture to?
NextPCB's standard process holds impedance to within ±10% of your target. For high-speed or noise-sensitive links that need a tighter margin, NextPCB also offers a ±5% controlled-impedance process — specify this when placing your order.
What's the difference between this calculator and NextPCB's Microstrip, Differential Microstrip, or Stripline calculators?
This calculator matches your target impedance to NextPCB's actual manufacturable stack-ups, so the trace width and spacing it returns are ready to order. The Microstrip Impedance Calculator, Differential Microstrip Impedance Calculator, and Stripline Impedance Calculator all use standard closed-form formulas (IPC-2141 for microstrip and stripline) on a single geometry you specify directly, independent of any particular fab's stack-up — useful for quick estimates early in design, before you've settled on a stack-up.
Can I calculate differential pair impedance with this tool?
This calculator is focused on single-ended impedance matched to NextPCB stack-ups. For differential pairs (USB, PCIe, HDMI, LVDS, etc.), use the Differential Microstrip Impedance Calculator.
I just want a quick single-ended microstrip estimate — do I need this full calculator?
Not necessarily. If you already know your trace width, dielectric height, copper thickness, and dielectric constant, and just want a fast IPC-2141 estimate for one external-layer trace, the Microstrip Impedance Calculator is quicker. Come back to this calculator when you want that target matched against a real, orderable NextPCB stack-up instead of a formula estimate.
What inputs do I need before I start?
Have your layer count, board thickness, outer and inner copper weight, whether the design needs blind/buried vias, and your target impedance and signal layer ready. If you already know your reference planes, you can enter those too.
Is the PCB Impedance Calculator free to use?
Yes, the online calculator is free. For full stack-up comparison, design rule checking, and exportable manufacturing reports, download HQDFM, NextPCB's free desktop DFM software.
How do I get a full stack-up and DFM analysis, not just a trace width?
Download HQDFM, NextPCB's free DFM analysis software. It covers complete stack-up design, impedance analysis across every layer, and a full design rule check before you submit your Gerbers.