# Is this a reasonable way to calculate my calories during commutes?

I’m looking at the the report calories burned from my Wahoo Elemnt and Strava and I think they’re complete BS. I think I myself can better estimate my calorie burn on a given commute.

Tell me if I’ve got any of the following wrong.

I have a rough idea of what it feels like to pedal 100w, 200w and 300w. I also know that when my HR is 120bpm on my trainer, the wattage will be around 150w.
My commute is just a touch over 30mins, and I think my avg. wattage is around 150w since my HR averages 120bpm.

Given 100w/hour = 360kj
=> 150w/hour = 540kj
=> 150w/30mins = 270kj
=> 270kj =~ 270kcals

Is there anything I’m missing?

1 Like

A power meter

Without that anything you’re doing is going to be guesswork

What you’ve got is a fine approximation, but it will always be guesswork when you’re basing it on RPE or HR

1 Like

It’s always going to be guesswork. But I’m just trying to figure out if my ballpark is better than Strava’s. Ultimately this is just to help calorie counting, so not massively important. Certainly not enough to invest in a power meter.

As ballpark figures they look ok.

1 Like

What kind of place is your commute? Mine is in London with a lot of stopping and starting, so I’m constantly doing little pushes well over threshold to get going, then cruising along behind other cyclists to the next light. Would be hard to estimate NP if I didn’t have my PM.

Mine is along a towpath alongside a canal so I have no stops at all. There are a couple of locks to ride up, I normally put it in the easiest gear and trundle up them. I’m guessing my NP and avg. power are virtually the same.

Wow, that’s like a dream commute for me. Steady pace so you control effort and body temperature in summer or winter, no traffic. Amazing.

1 Like

That’s also a perfect place for some workouts if you don’t have to stop!

Yeah I know, I have a pretty sweet deal. Only slight drawback is that it’s longer than if I were to ride on the road. Just means when the weather is bad I switch to the road and engage beast mode.

As much as I’d like to get training done whilst I’m commuting, it doesn’t really work for me. I get my quality workouts done on my trainer so the commutes make for perfect recovery rides. I’m also worried about efforts on the commutes affecting the quality of the time spent on the trainer. Besides the towpath is shared with pedestrians so it’s not fair to them or indeed other cyclists if I’m smashing it up and down going past them. I’ve had other cyclists buzz me and it to say I was annoyed is an understatement.

1 Like

I’m sure if you shout out “vo2 max!” as you approach they’ll understand and be more than happy to step aside.

4 Likes

I’m about 80 kg. Cycling at 150 watts I estimate 450 cal/hr, at 200 watts about 650 cal/hr, at 250 watts about 800 cal/hr. Be conservative in cals burned, I also est about 20 cal/km. at 200 watts.

Why go for 450kcal and not 540kj/540kcal? Is it purely to keep yourself below a certain amount of dietary calories?

I commute 4 days a week and I was concerned with them impacting my training time as well. My commute is 12 miles (-ish) each way, I usually drive in on Monday, leave my truck there all week and use it as a base of ops for storing clothes and such, then drive home Friday. Lately that’s been a little impacted with a job change where I have to be in early on Wednesdays but that’s the gist.

Right now I use tue/thu/sat as TR days and mon, wed, fri as ramp up and recovery days.

Like you, I’ve been trying to estimate the calories used on those rides, as well as the TSS with a goal of keeping it way down to allow me to focus on the TR days, and I agree the ELEMNT and STRAVA calculations were crazy before I put a cheap power meter on my commuter. I would ride 90 minutes (less than 1000ft of climbing) and get a TSS off 125 and 1300 calories burned. unlikely to say the least. What I did was buy a Stages FSA Power Meter and then put the matching Crank set on the Cross and Commuter bikes, so I can switch the meter back and forth. Works like a champ. At an hour ride home now I get about 450Kj and equivalent calories with a TSS more like 65. Same route.

This is an example of a wonky ride. The Kj is 460 the estimated calories is over 1000. At 118W average…

It makes me wonder what Wahoo is thinking with that calorie and TSS calculation. Something is throwing it off, but I have yet to figure what it was.

I was just estimating the calories burned based on my power meter and ergometer calculations to give you some comparative numbers.

The 467 kj seems right. 25 km at 20 kj/km gives you 500 kj. The FTP it is using to calculate the other numbers must be set too low.

1 Like

There’s a known formula for converting watts over time into kj. If you actually know your power numbers there is no need to estimate.

I believe it is something like kj = watts * seconds / 1000

So if you did a straight 200 watts for an hour that’d be something like kj = 200 * 3600 / 1000 or 720 kj. Since kj are approximately equal to calories you pretty much know your calorie expenditure

Therefore - don’t estimate your calorie burn unless you have to

It will be how your HR zones are configured on the ELEMNT? No? As far as I can tell Wahoo completely ignores power data and the cal/hr is calculated based on % of max hr. I think Strava used to apply their own calorie calculation but at some point last year they switched to simply taking kcals verbatim from the ELEMNT.

Anything Heart Rate based will depend on what zones you’ve input. My Bolt has defaulted away from the heart rate data I’ve inputted a couple of times, which skews the time in the different zones, which in turn skews the calorie burn.

fwiw, I haven’t found major differences between my Garmin watch and my Bolt. The Bolt is maybe higher on shorter rides than the garmin, but it evens out on longer rides. Both incomparable to what Strava or even the watch show without a HRM though!

Whether 100% accurate or not, I used the calorie burn as part of my weight loss strategy, and now my maintenance strategy - I just don’t try to eat all of the “earned” calories every time, particularly based purely off Heart Rate.

1 Like