I need to run 225 foot of wire from my main breaker panel to my shop to run a 220 volt table saw its 18 amp also what size breaker ? Thank you kevin also it will be under ground

Since you can only run one circuit or feeder to a detached structure I'd run a feeder to a sub-panel so you can have some lights and other receptacles.

For a typical residential wood shop a 50 or 60A feeder would be fine.
For that distance I'd run #4THHN/THWN conductors in conduit, from a 60A breaker in the house, to a small panel in the shop.

I posted a ? Yesterday about running 225 ft of wire to shop from house it was answered to use #4 thhn now wondering is the groud also #4 or is it smaller thanks kevin

***Threads Merged*** TKR

Use a #6 THHN/THWN green conductor for the equipment ground for this feeder.