Switching a 220VAC/20A Load with a 5VDC Coil Voltage?
Rather than guess at how much to oversize the relay, it is best to use a relay that is rated based on motor power. The IEC motor standards include a rating system that rates relays on more specific application information. In the USA, relays that are suitable for use with AC motors have a horsepower rating.

Look at my more specific answer to this more specific question: Max allowed inductive load (pump) for a given relay