what age and how?

what age do cats learn to go toilet outside? and how do i go about training him to do so? as i really dont want to have the cat litter box in house 4 the rest of hes life!

hes using one of those covered cat litter boxes and i live on the 1st floor so will have to go down stairs 2 let him in/out witch isnt a problem

[hes 12/13 weeks old by the way]

Personally I'd keep the litter tray. That way you can keep an eye on what he does in it and notice if there are any problems. If he always toilets outside it won't be so easy to notice if anything is out of the ordinary. You also run the risk of him annoying the neighbours by going to the toilet in their gardens. Once he does go outside though you might find he chooses to toilet outside of his own accord. You can encourage him to use the outside by gradually moving the litter tray nearer and nearer the door and/or putting some soil in the tray so that he gets used to using soil rather than litter.

But if he's only 12/13 weeks old he'll be indoors for a while yet as he'll need to be kept in until he's neutered.