It's not how far away they can smell you, it's what happens right after. It's been my experience that a deer will often stop, smell some more, become alert, snort, etc. Often they then turn and walk away. I've never seen a coyote linger at the smell of fresh human scent - as soon as they hit a track in the woods or get downwind they immediately sense danger and run.
I'm sure they could wind you from several hundred yards depending on conditions. Use their trust in their sense of smell to your advantage, especially if you use a decoy. They will typically circle downwind of a decoy/attractor. You can start planning a hunt by being even further downwind.