A simple creepage and clearance calculator, providing indicative minimum distances based on IEC 60664-1:2020 and ISO 21498:2021 table lookups with linear interpolation. It does not replace formal insulation coordination analysis by a qualified engineer. Always verify against the applicable standard for your specific application and jurisdiction. BatteryDesign.net accepts no liability for design decisions made using this tool.
High-voltage circuits can arc or flash across a gap. Whether that discharge travels through the air or tracks along a surface depends on geometry, voltage, and environmental conditions. Two distinct minimum distances are therefore controlled in HV design.
Both are defined in IEC 60664-1, the primary insulation coordination standard for systems up to 1,000 V AC / 1,500 V DC. For automotive battery systems, ISO 21498-1 and the VDA LV 123 standard also reference these principles. The purpose is to prevent two distinct failure modes: electrical breakdown across an air gap (clearance violation) and surface tracking along insulation (creepage violation).
Creepage — the shortest path between two conductors measured along the surface of an insulating material.
Clearance — the shortest path between two conductors measured through the air.
Worked Examples
| Standard | Voltage | PD | OVC | Material | Alt (m) | Expected creep | Expected clear |
| IEC 60664-1 | 800 V DC | PD 2 | OVC II | IIIa | 0 m | 6.30 mm | 6.0 kV impulse → 5.50 mm |
| IEC 60664-1 | 800 V DC | PD 2 | OVC II | IIIa | 3000 m | 6.30 mm | 5.50 × 1.235 = 6.79 mm |
| IEC 60664-1 | 400 V AC | PD 3 | OVC III | IIIb | 0 m | 8.00 mm | 6.0 kV impulse → 5.50 mm |
| ISO 21498 | 400 V DC | PD 2 | OVC II | IIIa | 0 m | 4.00 mm | 4.0 kV impulse → 3.00 mm |
| IEC 60664-1 | 800 V DC | PD 2 | OVC II | I | 0 m | 4.00 mm (Reinf: 8.00) | 5.50 mm (Reinf: 11.00 mm) |
Note on clearance for 800 V DC: 800 V sits in the 601–1000 V rated voltage bracket of IEC 60664-1 Table F.1. OVC II at that bracket gives a 6.0 kV rated impulse voltage, which requires 5.5 mm clearance (Table F.2, PD 2). This is higher than the 3.0 mm figure sometimes seen in automotive references, which use the mains supply voltage (e.g. 230 V AC → OVC II → 2.5 kV impulse) rather than the DC bus voltage to determine impulse level. This calculator applies Table F.1 to the working voltage entered, which is the correct approach for equipment rated at that voltage.
Appendix A — CTI Material Group Quick Reference
| Group | CTI range (V) | Typical materials | Common automotive use |
| I | CTI ≥ 600 | Glass, ceramic, PTFE, mica | HV connectors, power electronics substrate |
| II | 400 ≤ CTI < 600 | Phenolic, some PA66 GF | BMS connector housings |
| IIIa | 175 ≤ CTI < 400 | FR4 PCB, PP GF, PA6 GF, PBT GF | Pack busbars, module housings, PCBs |
| IIIb | 100 ≤ CTI < 174 | Unfilled PA, some polyester | Avoid in HV applications above 400 V |
Appendix B — Overvoltage Category Quick Reference
| OVC | Description | Automotive example |
| I | Protected from mains transients | Internal low-voltage circuits behind DC-DC converter |
| II | Equipment connected to fixed installation | Traction battery pack (BMS-protected, fused at PDU) |
| III | Fixed installation, special requirements | High-voltage PDU, main contactors, charging port |
| IV | At origin of installation | Vehicle inlet directly exposed to charger cable transients |
See also: Insulation and Isolation, IEC 60112, Comparative Tracking Index