Caymandiver1

I am wondering about the difference in calories burned calculated by cyclemeter vs strava
For example today after riding 40 miles at 17.2 mph avg cyclemeter says I burned 2500 calories while strava says I burned 1250. That's a huge difference.
Anyone know why and which one is more accurate.

Machka 

I use the formula 100 calories for every 5 km. I figure it's as accurate as anything else.

Using that formula, I'd calculate that you burned approx. 1300 cal. on your ride. So of your two choices, I'd say strava is closest.

DrIsotope

An app making an estimate off of rider weight and speed alone is just guessing. Adding a HRM will help the accuracy a bit, and a power meter will really improve the accuracy of the guesstimate. Strava without sensors (I've found) will always guess high. Garmin Connect is far more conservative. With a power meter, they're both within 10% or less. If you're trying to eat to maintain or lose weight, then in general, always trust the lower figure.

So if Strava is giving you half of Cyclemeter, then Cyclemeter must be just throwing it out there. Be sure to constantly keep your weight input updated, and keep your heart rate zones updated as well.

anotherbrian

I found Strava to be within ~10% of my power metered road bikes when riding a mix of hills and flats solo.

Strava can't account for drafting, so if you are getting a free ride at 26mph in a group, Strava (and anything that bases it on time and speed) will grossly overestimate the number.

Strava also relies on an accurate rider and bike weight, at least when they estimate power. If those aren't accurate the estimated power (which I expect calories is derived from) will be off (and I've found Strava to be accurate to a percent or two on long 4%'ish+ climbs).

gregf83 

How are you getting the Strava estimates if you have a powermeter. Strava normally uses 1.1 x kj recorded by your powermeter.

spdntrxi

correct and garmin connect I think uses 1.0x kj.

DrIsotope

I think he means the Strava estimate for non-PM bikes vs. the reported calories for PM-equipped bikes.

Pre-PM, Strava consistently underestimated by work done (estimated power/calories burned) by as much as 20%. I make a good bit more power than Strava guessed I would.

gregf83 

Strava must assume you ride in a more aero position than actual.

DrIsotope

It has my stats. It should know I'm incapable of defying physics.

But I did spend 6+ months with Gator Hardshells voraciously eating watts.

anotherbrian

I had Powertap wheels before I bought a Tarmac with disc brakes, and was trying to decide if I really needed another power meter (also started riding a fixed gear heavily at the same time). First I compared a standard route that I've ridden dozens of times over the years to see what the measured average power (Strava's NP'ish number that is under the Distance on the activity page) was vs the estimated, then stripped the <Watts> from the TCX file exported from Garmin Connect, changed the <Id> value so it wouldn't clash, and re-uploaded it. * For the most part they were all close -- at least close enough that I decided I'd be fine using Strava's estimated NP'ish number as the basis for a TSS I could use for the PMC in Golden Cheetah.

Ultimately I did buy Powertap pedals for the Tarmac, and my experimenting ended, but I was convinced enough of their estimates that I'll use it for future TSS's if I don't have real data.

anotherbrian

My "* For the most part" was because for some efforts, like 297W for 57:27, Strava was completely wack, estimating the power at 225W. My gear was set to a 20lbs road bike though I was riding a Diverge with 28mm Conti 4000S's, but it took turning it into a 30lbs cross bike before the numbers aligned.

My "For the most part" were rides that had NP's of ~225-250W.

gregf83 

Strava provides average power and weighted avg power. The weighted avg power is similar to NP but a little lower. If you don't provide power data, Strava will estimate the avg power but they don't estimate the weighted avg power so I think you were comparing different numbers. Also, not clear why you'd want to use Strava's NP'ish number in GC vs just feeding the raw data into GC directly.

Carbonfiberboy 

If you don't have a PM, Strava estimates kJ by running the equations of motion on your ride. Accuracy therefore depends on the accuracy of the user's inputs and of course it ignores drafting and surface winds. HRMs and other computer outputs are notoriously inaccurate. IMO the reason for such inaccuracy is simply marketing. No one wants an instrument that shows they worked out for an hour and only burned 100 calories. Sad.

Harvieu25

For a certain ride, my Polar FT7 would show 1800-1900 calories burned where my 520/Strava/Connect show almost 2/3's of that. No big deal as I wasn't gaining/loosing before...

Rowan

I am happy with what Strava provides me (except the altitude gain figures which are totally whacko). But I use them for comparative purposes and for fun. I am not tied to analysing the nth degree of data for my rides... I enjoy much more most of the other aspects of them. The calories burned correspond quite well with Machka's estimates formula above, and my weight loss and maintenance correspond as well.

Having said all that, I did achieve 41 personal records on segments during a 77km outing yesterday! So there must be some improvement in my speed and fitness...

anotherbrian

[Update: I accidently cropped out part of the ride before posting to Strava without the power data ... just re-did it, and updated the kJ's Strava calculated]

As mentioned in my original post, I don't have power meters on all of my bikes. I do use the Coggan Performance Manager Chart in Golden Cheetah though, so having TSS's for my rides is necessary. For bikes without the power meter, Strava's Estimated Average Power / FTP * Moving Time has given me a TSS within ~10% of what my power meter actually measured for the ride.

Here's an example from yesterday (I can PM folks links to the activities if they'd really like to see them), for a 60mi ride, 5200ft of climbing, 75% pavement, 25% gravel and singletrack, 4h48min moving, 5h45m elapsed:

Powertap P1: 2881kJ
Strava calculated: 3086kJ (strikeout the 2939kJ)

That's closer than I'd seen for my previous faster-paced road rides (those are within ~10%), but reinforces my belief that Strava is doing a good job estimating the work (and power) with distance, speed, and elevation.