I posted awhile ago about not being able to trust RunKeeper’s calorie numbers. I was wrong, and I’ll explain why I was confused with the numbers I was seeing and what you have to do to make the numbers reflect reality. Before I get into it, keep in mind that the numbers are an estimate. Every time you get better data about the physical activity, the better the estimate about calories burned will be, but it will never be totally accurate.

The problem I had was that when I recorded a walk, run or bike ride, the calorie count would change drastically after saving the activity. This is because the mobile app does it’s own best-guess about the calorie count based on distance and pace, but knows little about terrain. Once the app sends the data up to the RunKeeper servers, the caloric burn rate for each segment of the trip is weighted based on the severity of the slope through the path taken. This means it’s a lot more accurate than it was, and gets you closer to a true number.

However, be careful. I’ve found that the GPS data RunKeeper saves isn’t terribly accurate. The same walking loop that I take at lunch is usually recorded at 5+ miles, and there’s a huge variation every day. Looking at the actual recorded walking path, it would appear that I’m teleporting around and walking through solid walls, houses, and other obstacles. All of these count towards my distance and my calories burned. This is a huge problem, but I’m not sure how much RunKeeper can do to fix the data Apple is giving them from Location Services. :(

My work around until this gets better is to go to the RunKeeper site and manually add the path I’m walking. As I almost never deviate from that path more than about 18 inches side to side, and I’m walking at the edge of the road, it’s safe to use the “stick to roads” option in their editor. Once you are done, you can change the input type in the mobile app from “GPS” to “Manual”, and pick your saved route. Incidentally, my 5+ mile walk is really a 4.2 mile walk, looking at the road data. I’m also burning 300 or so “less” calories a day, but what it means is I’m getting better data than I was before. Better data is more accurate data, and lets me plan my meals better.

So, again, sorry for dissing on RunKeeper. Now that I know how it works, it makes a lot more sense what it was doing, and my trust has been restored.