Each capacitor is designed for a particular rated voltage, which it must stand up to without adverse effect during continuous operation.

However, this only applies to ambient temperatures of < +85°C; at higher temperatures the maximum permissible voltage or voltage limit for continuous operation is reduced by voltage derating.

This is caused by tiny weak points in the dielectric, which, under increased temperatures, are subject to greater stress and can then break down.

In the case of rated voltage, DC voltage specifications are distinguished from AC voltage data. In general, this information is printed on the capacitor with clear symbols; in the case of capacitors with very small dimensions code symbols may be necessary as with the tolerance specifications.