Best ways to track running mileage & pace

Buy a note book.

Cheapest and most reliable running tracker ever.

I should add that it would ideally export data easily to excel/csv, but that's not really essential.

I run a lot of random roads and trails where mileage is unknown, hence the GPS focus.

The Strava app is a decent option or MapMyRun. Just set all of the social settings to private and you've got what you need.

Though personally I have to admit, if I were you I'd just go off time and effort and chart weekly minutes/hours instead of mileage.

You sound interested enough in stats that you should just go ahead and buy a GPS watch. The HR function on recent models is accurate enough. A midrange Garmin 245 will give you plenty of numbers to analyze, and you can export each activity as a .csv file.

Thanks all. I might go ahead and buy a Garmin. If nothing else, it might help me stay motivated if I have more numbers to play with.

Agreed about tracking minutes/hours of effort instead -- there is a lot of benefit to that, and it's why I switched in the first place. At this point, though, I need to get back to a point where I can tell what 7 minute versus 8 minute versus 9 minute pace roughly feel like. I was deceiving myself in terms of my fitness level for the last year, and I don't like that.

A Garmin would help but I’ve been applying a perceived exertion score for my runs and multiplying that by the miles I ran that day. This gives me a gauge of total training stress for the week. Some may try to apply some logic to the perceived exertion score (like Strava...1-3 is I could talk easy, 4-6 is moderate breathing, etc...) but I found just a dumb “How did that run feel?” To be best in a training cycle. Even though a run may be “breathing easy”, if you still feel like ass and it feels hard for whatever reason then that’s a much bigger stress and should be scored higher. This has helped me track and moderate effort and know when to cut short, modify, or even skip a day to keep my effort for the week in check.

A watch and an odometer and/or map. They've worked just fine for me for over four decades.

For Christmas in 1984 I got a subscription to Runner's World. With that subscription I got a 1985 running log book. I still have it and I pretty much used it for the whole year. Anyway, that type of log book works great. Never need electricity to operate it. It won't crash. Don't need to save it to a thumb drive etc.