# FR4 PCB thermal expansion online calculator

Calculate the thermal expansion in millimeters (mm) of a FR4 PCB in X/Y direction. A typical temperature difference default is 65°C, the difference between 20°C room temperature and the max temperature rating of 85°C parts. The default 13ppm/°C thermal expansion coefficient is from this website.

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[calculator]

[calculator-input name=“l” label=“length” unit=“mm”][/calculator-input] [calculator-input name=“delta_t” label=“temperature difference” value="" unit="°C"][/calculator-input] [calculator-input name=“tcoeff_ppm” label=“temperature coefficient” value=“13” unit=“ppm/°C”][/calculator-input]

[calculator-expression name=“expansion_ppm” formula=“tcoeff_ppm*delta_t” unit=“ppm per 1”][calculator-expression name=“thermal_expansion” formula=“l*expansion_ppm/1e6” unit=“mm”][calculator-expression name=“thermal_expansion” formula=“l*expansion_ppm/1e6” unit=“mm”][calculator-expression name=“thermal_expansion_percent” formula=“thermal_expansion*100/l” unit=“mm”]

[calculator-output name=“thermal expansion” unit=“mm”] A FR4 PCB with a length of of <%= formatFloat(l, “mm”) %> and a thermal expansion coefficient of <%= formatFloat(tcoeff_ppm, “ppm/°C”) %> will expand by <%= formatFloat(thermal_expansion, “mm”, 5) %> (<%= formatFloat(thermal_expansion_percent, “%”, 5) %> of the original length) over a temperature difference of <%= format(delta_t, “°C”) %> [/calculator-output]

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