Creepage Distance Calculator
Estimate a recommended creepage distance (in mm) for PCB and insulation design based on voltage, pollution degree, material group, and insulation class.
What Is Creepage Distance?
Creepage distance is the shortest path between two conductive parts measured along the surface of an insulating material. On a printed circuit board, this path follows the board surface between two copper features at different potentials.
Why it matters: contamination, moisture, and dust on surfaces can create leakage paths. If creepage is too small, insulation can degrade, carbonize, and eventually fail.
Creepage vs. Clearance
Clearance
Clearance is the shortest distance through air between conductive parts. It is strongly affected by altitude and surge transients.
Creepage
Creepage is measured on the insulating surface. It is influenced by pollution degree and material tracking resistance (CTI/material group).
Designs often fail compliance when one distance is correct but the other is overlooked. Always verify both during safety review.
How This Calculator Works
This tool uses a practical engineering model based on common IEC-style creepage behavior:
- Starts with a base creepage estimate from working voltage.
- Applies multipliers for pollution degree and material group.
- Adjusts for insulation class (basic vs reinforced).
- Adds an optional design margin for manufacturing tolerance and aging.
The result is a useful planning estimate for early design and PCB routing decisions.
Quick Reference: Typical Inputs
| Use Case | Typical Pollution Degree | Material Group | Insulation Type |
|---|---|---|---|
| Consumer indoor electronics | PD2 | IIIa / II | Basic |
| Industrial control cabinets | PD3 | IIIa / IIIb | Basic or Reinforced |
| Medical / safety-isolated interfaces | PD2 | II / I | Reinforced |
| Outdoor or very harsh contamination | PD4 | IIIb | Reinforced |
Practical PCB Layout Tips to Improve Creepage
- Move high-voltage nets to opposite board sides and keep generous separation.
- Use slots or grooves in the PCB to increase effective creepage path length.
- Avoid solder mask as your only insulation strategy for safety-critical barriers.
- Route contamination-sensitive gaps away from connectors and board edges.
- Document your assumptions (pollution degree, CTI, insulation class) in design files.
Frequently Asked Questions
Does conformal coating always reduce required creepage?
Not always. Coating may help in practical reliability, but safety standards treat it differently based on process control, coating type, and certification path. Use it as an improvement, not a guaranteed substitution unless explicitly approved.
Can I use this as a compliance certificate?
No. This is a design calculator, not a formal approval report. Final values must come from the specific standard and edition relevant to your product category.
What standard should I check for final numbers?
Many products reference IEC 60664-1 principles, but end-product standards (for example medical, lab, EV, IT/AV, appliance standards) may set different requirements.