Understanding the 1-in-60 rule for navigation

Can someone explain the 1-in-60 rule in plain terms? I keep seeing it mentioned in navigation study material but I'm not sure when I'd actually use it in flight.

The 1-in-60 rule states that a 1-degree error in track over 60 nautical miles results in being 1 NM off course. You can use it to estimate track corrections in flight. For example, if you've flown 30 NM and you're 2 NM off track, your track error is about 4 degrees (since 2 NM offset at 30 NM distance is 2/30 * 60 = 4 degrees). You'd then double the correction to regain track if you're halfway to your destination.

Oh right, so you can use it to figure out both how far off you are AND what heading correction to apply. That's very practical. Is it accurate enough for real-world navigation?

It's an approximation based on the small-angle property of trigonometry, so it works well for errors up to about 15 degrees. Beyond that it starts to drift, but for typical VFR navigation corrections it's more than adequate. It's especially useful if you don't have a GPS and are relying on map reading and dead reckoning.