How do u tell a guy that you don't want a relationship with him without hurting him?

I wouldn't have thought that telling someone that you don't want to be in a relationship with them would send them into a fit, unless they take it really badly, but even then...

Tell him straight that you're not interested in dating him. There is no good dancing around it and trying to avoid the matter. The longer he thinks that he has a glimmer of hope of getting together with you, the worse it will be when you tell him that your not interested in taking the friendship to the next level.

Tell him somewhere public, like a cafe, or maybe even a pub. Make sure that you tell him that it is only for a drink and that you have something that you would like to talk to him about. Don't tell him at work. This would make it really difficult for both you and him, especially for him if your work colleagues hear you telling him. He would never hear the end of it.

Jam it back in, in the dark.