Since Dunder2004 recommended plotaroute.com in a post earlier, I've spent some time poking it.
First I plotted my latest route, to see if the site distance tallied with the results from my Garmin - it did, showing just under 4 miles for 3 laps of my route round the village.
Then I thought I'd plot a potential route I've been thinking about, but that I thought was way too long for me - out of the village, to the next village, round the countryside and back into my village.
Turns out it's pretty much the same distance, just under 4 miles!
To sit and think about it, it seems like much further.