help in working out a radius

I'm trying to work out the radius of an area but have no idea what i am doing.
For example: We're moving interstate and i am trying to find a house that will be within a 30 minute radius from work how to i work that out on a map?
For example: We're moving interstate and i am trying to find a house that will be within a 30 minute radius from work how to i work that out on a map?