PCB Creepage Distance Calculator
Estimate preliminary PCB surface creepage spacing from working voltage, pollution degree, CTI material group, and basic or reinforced insulation requirements.
This tool uses a simplified IEC 60664 and IPC-style screening table for early layout work. It is not a certification database or substitute for the applicable product safety standard.
Engineering tool
PCB Creepage Distance Calculator
Estimate preliminary PCB surface creepage from voltage, pollution degree, CTI material group, insulation type, and a project correction factor.
RMS, DC, or recurring peak working voltage as defined by the applicable standard.
Project-specific multiplier. Altitude normally affects clearance more directly; verify whether it applies to creepage.
Result console
- Recommended creepage distance
- 2.5mm
- Adjusted creepage distance
- 2.5mm
- Selected voltage band
- 250V
- Correction factor
- 1×
Safety status
Screening Pass
Basic insulation • PD2 • Material Group IIIa
Use the adjusted value as a preliminary layout minimum only. Confirm working-voltage definition, overvoltage category, CTI, coating, altitude applicability, and product-specific requirements.
Formula reference
Simplified Creepage Rules
The calculator selects the next supported voltage band, applies pollution-degree and CTI material factors, doubles the result for reinforced insulation, then applies the user-supplied project correction factor.
Recommended creepage = table value × pollution factor × material factor × insulation factorReinforced insulation factor = 2Adjusted creepage = recommended creepage × correction factorVariable definitions
- Voltage bands
- 50, 100, 150, 250, 400, 630, and 1000 V
- Material groups range from high-CTI Group I to lower-CTI Group IIIb
- Altitude usually modifies clearance more directly than creepage; verify standard applicability
Worked Example
For 250 V working voltage, Pollution Degree 2, Material Group IIIa, and basic insulation, the simplified table recommends 2.5 mm creepage.
With an explicit correction factor of 1.0, the adjusted value remains 2.5 mm. Manufacturing tolerance and product-specific requirements should be added during the safety review.
Engineering Notes
- Creepage is measured along the insulating surface.
- Clearance is measured through air and follows different rules.
- Pollution degree and material CTI strongly affect required creepage.
- Safety-critical products require review against every applicable product standard.
- Slots or insulating barriers can increase the effective surface path when permitted by the standard.
Support reference
FAQ
What is PCB creepage distance?
Creepage is the shortest path between conductive parts measured along the surface of an insulating material such as a PCB substrate.
What is the difference between creepage and clearance?
Creepage follows the insulating surface, while clearance is the shortest distance through air. They use different rules and environmental correction factors.
How does pollution degree affect creepage?
Higher pollution degrees represent more conductive contamination or condensation risk and generally require larger surface spacing to prevent tracking.
Why does CTI material group matter?
Comparative Tracking Index describes resistance to surface tracking. Higher-CTI materials, such as Group I, can often use smaller creepage distances than lower-CTI Group III materials.
Can this calculator be used for product certification?
No. It is a simplified layout-screening estimate. Certification requires the exact product standard, IEC or UL tables, working-voltage definition, overvoltage category, environment, material data, and approved construction.
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