How much can ovulation vary?

If you have a relatively regular cycle, by how many days does your ovulation day vary?

I’ve decided that this month I’m not using OPKs and just go with the flow. I ovulated on cycle day 17 last cycle with an overall 30 day cycle.

I know ovulation varies but should I expect to ovulate +/- 2 days from the last cycle day I ovulated? Can anyone give me any pointers? I’m really just trying to figure out my fertile window.