Raising my rates

I am planning to raise my rates soon. My current rate is $58.50-65/hour. I am debating raising to $75 or $80 and unsure if $80 is too high or too drastic of a change. But part of my plan is to actually *lose* a few clients, so maybe it’s actually good to go higher? But then, I don’t want to lose *all* of my clients. How do I decide what is a good rate to raise to? I don’t plan to justify the rate increase to my clients either way; I will just give them notice. Background info: I know for sure that my current rate is well under the “going rate” in my industry for my area.