PCB Clearance Distance Calculator
Estimate preliminary PCB through-air spacing from operating voltage, pollution degree, overvoltage category, altitude, and design margin.
This simplified IEC 60664 and IPC-style screening tool supports required-clearance, maximum-voltage, and existing-gap checks. It does not replace certification analysis.
Engineering tool
PCB Clearance Distance Calculator
Estimate preliminary through-air PCB spacing, reverse-check voltage bands, or compare an existing air gap.
Result console
- Required clearance
- 1.5mm
- Recommended clearance
- 1.8mm
- Altitude correction factor
- 1×
- Safety margin
- 20%
Clearance status
Preliminary Estimate
Use the recommended value as preliminary layout spacing only. Material Group is recorded for coordination with creepage review but does not alter this simplified through-air clearance estimate.
Formula reference
Simplified Clearance Rules
The next supported voltage band is adjusted by pollution degree, overvoltage category, altitude, and the selected safety margin.
Required clearance = table spacing × pollution factor × category factor × altitude factorRecommended clearance = required clearance × (1 + safety margin)Check ratio = existing clearance / recommended clearanceVariable definitions
- Voltage bands
- 50, 100, 150, 250, 400, 630, and 1000 V
- Altitude factor is 1.0 through 2000 m and increases in steps through 6000 m
- Material Group is recorded for creepage coordination but does not change this air-gap estimate
Worked Example
At 250 V, PD2, CAT II, and 2000 m, the simplified required clearance is 1.5 mm.
Adding a 20% margin produces 1.8 mm recommended clearance. An existing 3 mm gap passes this preliminary screening check.
Engineering Notes
- Clearance is measured through air.
- Creepage is measured along the insulating surface.
- Higher altitude reduces air breakdown strength and may require larger clearance.
- Pollution degree and overvoltage category affect safety spacing.
- Safety-critical products require review against the exact applicable standard.
Support reference
FAQ
What is PCB clearance distance?
Clearance is the shortest through-air distance between conductive PCB features. It helps prevent arcing and dielectric breakdown.
What is the difference between clearance and creepage?
Clearance is measured through air. Creepage follows an insulating surface, so its requirements depend more directly on CTI and surface contamination.
Why does altitude affect clearance?
Air density and dielectric strength decrease with altitude. Above the standard reference altitude, a larger air gap may be required for the same withstand voltage.
What clearance is needed for 250 V?
There is no universal value. This simplified PD2, CAT II example starts at 1.5 mm before safety margin and altitude correction, but the applicable product standard may require a different value.
Can slots or barriers reduce clearance requirements?
Slots and barriers can change electrical paths, but they do not automatically reduce the shortest through-air distance. Their treatment must follow the exact applicable standard and construction rules.
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