Calculator
Estimate minimum PCB spacing for electrical safety design. Results are an engineering aid and should always be verified against your product standard and certification requirements.
What this calculator does
This tool estimates two critical insulation distances used in electrical product design: clearance (through air) and creepage (along an insulating surface). These distances help prevent arcing, tracking, and insulation failure in power electronics, control boards, battery systems, and mains-connected devices.
The calculator uses practical engineering approximations inspired by common safety standards such as IEC 60664-1. It is best used early in concept design to size board spacing, connector pitch, slotting, and package placement.
Clearance vs creepage (quick refresher)
Clearance distance
Clearance is the shortest line-of-sight distance through air between two conductive parts. It is mainly affected by voltage stress, transient environment (overvoltage category), pollution level, and altitude.
Creepage distance
Creepage is the shortest path along the surface of an insulator between conductive parts. It is strongly affected by pollution degree and material tracking resistance (CTI group), in addition to working voltage.
How to use the calculator
- Enter the highest continuous working RMS voltage present between conductors.
- Select the correct overvoltage category for your installation environment.
- Choose pollution degree based on expected contamination and condensation risk.
- Pick your PCB or insulation material group from CTI data.
- Set altitude for the final operating location.
- Select basic or reinforced insulation.
The output gives recommended minimum distances in millimeters. In production designs, you should include manufacturing tolerance, contamination margin, and aging margin beyond the bare minimum.
Design notes and practical tips
1) Use slots to improve effective creepage
Routed slots or barriers can increase path length along the surface without growing the whole board outline. This is especially useful in compact SMPS designs.
2) Watch component body geometry
Even if copper spacing is compliant, package shape and lead standoff can reduce practical insulation distance. Always verify 3D geometry around high-voltage nodes.
3) Altitude matters more than many teams expect
Designs that pass at sea level can fail at higher elevation due to reduced dielectric strength of air. If your product is shipped globally, consider worst-case installation altitude.
4) Conformal coating is not a free pass
Coating can improve robustness, but standards impose specific conditions before reducing creepage/clearance requirements. Do not assume automatic spacing reductions unless explicitly allowed by the governing standard.
Standards and compliance context
Depending on product class, common references include:
- IEC 60664-1 (insulation coordination)
- IEC 62368-1 (audio/video/ICT equipment)
- IEC 61010-1 (measurement, control, lab)
- IEC 60335-1 (household appliances)
- UL 840 (insulation coordination)
Final compliance decisions are made using the exact edition of the applicable standard, product use case, and certification-body interpretation.
FAQ
Can I use this as a certification report?
No. This is a pre-compliance engineering estimator, not a substitute for formal safety evaluation.
Should creepage always be larger than clearance?
Often yes, but not always by a fixed ratio. In many practical low-pollution designs creepage ends up larger, while high-altitude conditions can drive clearance significantly upward.
Does reinforced insulation simply double spacing?
In simplified early design estimation, doubling is commonly used as a conservative rule of thumb. Actual standard tables can be more nuanced; always verify against the precise requirement.
Bottom line
Clearance and creepage spacing are foundational to safe, reliable high-voltage design. Use this calculator to move fast during architecture and layout, then lock final values using the exact standard and a documented compliance review.