PCB Clearance & Creepage Calculator

Clearance is the shortest air distance between two conductive parts, critical for preventing arcing or flashover. Creepage is the shortest path along the surface of the insulating material (e.g., solder mask or bare FR-4), essential for resisting tracking under contamination or humidity. Both are safety-critical dimensions defined by standards like IPC-2221 and IEC 60950.

This tool implements IPC-2221B (Section 6.3) for generic PCB design and IEC 60950-1 (Annex G) for IT/AV equipment safety compliance. It applies appropriate derating factors for altitude, pollution degree, material group, and conformal coating per both standards’ requirements.

Pollution Degree classifies the environmental contamination level: PD1 (clean, dry labs), PD2 (normally clean, occasional condensation), PD3 (conductive dust, rain, or persistent humidity). Most commercial indoor electronics use PD2; industrial or outdoor designs typically require PD3 — always verify with your end-use environment.

At higher altitudes (>2000 m), reduced air density lowers dielectric strength, increasing required clearance (but not creepage). This calculator applies the IEC 60950 altitude correction factor: multiply base clearance by 1.0 for ≤2000 m, 1.47 for 5000 m, etc. Altitude has no effect on creepage unless specified otherwise in special applications.

Conformal coating (e.g., acrylic, silicone, or urethane) improves surface insulation and allows reduced creepage distances per IPC-2221 Table 6-1. Enter “1” if the board will be fully coated *and* the coating is rated for the operating voltage and environment. Note: coating does not reduce required clearance—it only affects creepage.

Material Group defines comparative tracking index (CTI): Group I (CTI ≥600 V), Group II (400–599 V), Group III (100–399 V). Standard flame-retardant FR-4 typically falls into Group III (CTI ≈ 150–170 V); high-performance laminates (e.g., polyimide or specialized FR-4) may qualify as Group II. Always confirm CTI from your laminate datasheet.

This calculator uses the full IPC-2221B equations (including interpolation and altitude/pollution derating), not just table lookups. Minor differences arise from rounding, continuous interpolation between voltage ranges, and application of real-world modifiers (e.g., coating, altitude). For formal certification, cross-check with the official IPC-2221B tables and your AHJ’s interpretation.

Yes—but with caution. The calculator defaults to RMS AC voltage per IEC/IPC conventions. For DC systems, use the *peak* equivalent voltage (e.g., 400 VDC ≈ 400 V_dc — consult IEC 61800-5-1 or UL 62368-1 for DC-specific multipliers). Always validate against applicable HV standards and perform worst-case transient analysis.

Yes. External conductors (top/bottom layers) face harsher environments and require larger clearances and creepages than internal layers (buried between planes). This calculator outputs *minimum external* values. For internal traces, IPC-2221 permits ~50% reduction—confirm with your fab and safety certifier before applying reductions.

Calculate clearance and creepage separately for each unique voltage pair (e.g., 3.3V-to-GND, 230VAC-to-GND, 230VAC-to-3.3V). The highest resulting value governs spacing between those nets. Isolation barriers (e.g., slots, cutouts) must meet the largest required creepage across any adjacent conductors—not just the nearest pair.