What size wire to use to install an 220 volts electric dryer at 30amps?

Should have posted in Electric and Lighting.

The cable size will be # 10 wire. If dryer has a four prong plug (most likely) the cable will be 10/3 (3 conductors and a ground).

If dryer has 3 prong plug, the cable will be 10/2.

Any new cable installed for a dryer must be 4 wire, no matter what the dryer may have as a cord, if the dryer came with a 3 wire cord it will need to be changed to a 4 wire.