Figuring Mileages

When using Google Maps, you can modify the route if you don't like what Google comes up with.

If you look at the highlighted route, there are white dots, grab and drag one to the route you want and it will redo the route. Sometimes you may need to do 2 or 3 if it keeps trying to push you back to a freeway route (the routing logic give preference to staying on major roads).

We've never had an issue with the route lengths being incorrect. Do make sure you are comparing apples to apples. If you just enter the city names on Google Maps and put in the exact street address on your garmin, it will come back with different results because you asked for different start and end points.

I'd try to figure out what was different in the routes, between what planned on Google and what you drove. If the routes were actually the same I'd expect miles to be the same, or at least close.

Then I'd try to tweak the google route to match the driven. That's easy. I often explore alternative routes, not just the ones the GM suggests. For long distance drives, I find I really have to take major detours to change the mileage significantly (more, say than an hour's drive).

Matching times may be harder, since that depends not only on distance, but on estimated speed, which may vary with the road condition. In fact I use time vs distance to judge whether one route has slower roads than another - e.g. freeway or not, curvy or not, mountain or not. Speed estimates though are always rougher.

Garmin also has some online mapping tools. I've only dabbled in those, since the only Garmin I have is a watch.

Don’t blindly follow the Garmin without verifying the route. My old Garmin once took me to a rocky low water crossing when it should have had me turn about a 1/4 mile before that. Another time, a different Garmin tried to take me around to the back entrance to the Great Sand Dunes on an unpaved 4 wheel drive vehicle only road. Fortunately I knew better.

A general rule of thumb. Use whatever method you want to determine distance. Divide total distance by 50 and you will get a pretty accurate time that includes stops.

I use the google map millage and ajust the speed for less. So if its a 70 mph zone, im only going 65. So i divide the miles by 65 or 60 and then as above add an hour for stops, depending on fuel and how far im going. Unfortunately, millage, fuel, stops and traffic all add time. The miles for both maps should be similer. The times may be different.

I do my travel planning on the computer as well, I use distance tracker at

https://www.distancesfrom.com

Its pretty close but I add an hour at least for rest stops and gas etc. Its free. I also use google maps and AAA trip tik maker. Half the fun is the planning :)