How long till I can let my cat out of the house?

It depends where you live, If you live by a busy road, then wait about 2 weeks. If you live in a quiet place, wait 5 days to a week depending on how confident your cat is.

When you do let it out, You should lead it around the back yard on a wee leash for about 10 minutes. The let it off the leash and stay outside with it. Put some of its toys in the back yard or an unwashed jumper of yours that smells like you out there, to give it a sense of familiarity.

When it goes away, call it in about 10 minutes and it will come back, reward it with a treat. This will help it recognize home and also teach it to come when called. Leave something on your fence or by your gate that it will recognize the smell of. Maybe even just spray the grass with a bit of your perfume/ deodorant or if you have an air freshener with a smell that you have used for a while- that will work too. It will be able to smell it from a while away and will recognize the smell as home.

Make sure it stays inside on the first night you let it out, and the second night too if you can.