How much to pay a sub-contractor

Depends how much of the work they're doing! I'd imagine they'll have an hourly rate for freelance work that they'll either want to work to or will provide a quote for the job based on it.

Are they doing the design and you're doing the development (or similar), ie. are you each bringing separate skills to the job? Or are you subbing out tasks that you might normally do if you had capacity? If the former you'll likely be each quoting your part of the job and then combining them. If the latter, it's more a case that you're marking up their rate (up to you how much you reckon is an appropriate percentage).

However you do it, make sure you have a sufficient margin to make a worthwhile profit and make sure you leave some meat on the bone for the person you're subbing the work to. Fail to do either of those and it can come back to bite you.

Thanks for the reply.

Its a new dev learning. I have given him the specific task of making the css responsive - which I would noramlly do but just too busy. In this case he needed virtually no support, did a good job, in a good time. I think this relationship is likely to grow, but am testing it out. I quoted for responsiveness before he came along so I have a set figure for that part of the work. I figured on giving him 60% and keeping 40% for me.

Is that too generous??? Or is that about right do you think?

If he was taking on a whole role - say the whole build, I would get him involved in quoting from the start, and just add a little on for project managing.

I suppose I was just wondering what other people did so as to get a feel for what was 'acceptable/fair' I don't want to work for nothing, and I don't want to pay him too little.

Edward