How accurate is Strava?
 

Hello guys! I was just looking over some of my old rides on Strava and I noticed that my power outputs seemed a little high.
I weigh ~120-125lbs and my bike weighs 21 pounds. I'm only 16 and have not been seriously riding for long(beginning of summer).
Here is a ride I did a while back: http://app.strava.com/rides/1982942

My average wattage is 190W on the ride. Is this what you would expect a person to make? Or is it higher than what you would expect? Thanks!

P.S. Don't make me feel bad or tell me how much I suck, I already know. :D

Something is probably screwy with your segments - it's listing 300 watts for the Mulholland DESCENT, which I doubt you're actually doing unless you're going up, but your speed is 29mph. So some of your segments are probably screwy, but a 190watt average actually sounds about right for overall.

I've done most of the climbs on your route, and those are legit mountain climbs. A 14.5 mph overall speed on that terrain is actually very respectable. When I'm averaging 15mph for the same 5000ish feet of climbing on the same roads you're doing, I can pull a 21mph solo average for the 40ish miles from Santa Monica to Trancas INCLUDING stops for lights on the PCH, out to Trancas, which still has a good 1000ft of climbing en route. Which means I'm closer to 22-23 the entire way - that's fast enough to past most riders on the PCH and even catch some of the road racing pacelines (if I tag onto a fast paceline, I'll find myself doing 24 for a similar effort with the draft.)

What you can do is pick a climbing segment that has a ton of riders and look at its leaderboard by the <125lb weight class. Find the closest person to you on the leaderboard who has a lightning bolt icon. That icon means the person actually had a real power meter. That may give you an idea on accuracy. On long climbing segments (where it should be most accurate) it's probably within 15% most times. On flat or descending segments I'd just ignore the wattage number it guesses.

I'd say your average power probably is between 170-190 watts, very respectable speed considering that climb

Without a power meter the numbers don't mean much.

I did a similar ride last weekend that was 44 miles and over 5k feet of climbing. My average power was at around 180-190w (typing this on my iPhone I'll post my strava link tomorrow for comparison when I'm on my actual PC). I have an actual power meter on my bike and weigh 195. Because I weigh much more than you I probably put out a lot more power to do a similar ride. At 125 pounds it's probably safe to say you weren't putting out 190w.

Still an impressive ride for a 125 lb 16 year old! Good work!

off topic, but does anybody know how accurate their gradients are for climbs?

Anybody know how they go about estimating the calories burned on Strava? Not sure how they would know this without heart rate numbers. I wear a HR monitor and it always tells me I burned way more calories than what Strava tells me.

They figure mine out by using the kilojoule number from my power meter.

They estimate the power, which has a direct correlation to calories burned. As the OP states, the question is: how accurate are the power numbers? I'd say they're certainly not exact, but at least in the ballpark, as long as they have correct elevation data.

So the calories and power depend on how accurate the elevation data is?

nope they're not very accurate at all. i've had hills that were 30 watts off my real (measured with a powertap) wattage. BAsically just dont pay attention to it.

I weight about as much as you and on my ride today I went up a few climbs so you can look at my climbing rate and watts on those climbs and compare to yours if you want http://app.strava.com/rides/2178506

all strava knows are distance, time, and elevation change. from this it calculates speed and grade. you tell it your weight and it calculates an estimated power output.

it doesn't know anything about wind, your position on the bike, rolling resistance for your tires/tubes, smoothness of pavement, etc. if you're climbing a really steep hill, the numbers will probably be decent, since those other factors don't contribute as much in that situation. but if you're riding on flat roads, if it's really windy, if the pavement is crappy, etc., it's not very accurate.

Power estimates will depend on if you're climbing or not. If they have no elevation data, and assume you're not climbing when you are (or the opposite), then yes, it depends on how accurate the elevation data is.

Strava puts my 5 min power at 582W and my 10 min power at 422W...... I think that every now and then they go off the mark. But otherwise I think they are actually relatively accurate.

I've found Strava to be extremely inaccurate. I don't have absolute hard data on that as I don't have a power meter, but I often see stretches of my rides where I was doing 25-27mph on a flat and Strava somehow calculated 0W. Then it'll shoot up to 400W and sit there for a few minutes with absolutely no change in elevation whatsoever.

To be honest I pay no attention to Strava's power estimations, they just don't have enough information to determine accurate numbers when I have a total of 400ft of elevation gain over a 70 mile ride. :) This is also why I suck at climbing.

Here in the PacNW, we are either going up or down. Flat is a four letter word not in our dictionary. I've run climbing segments with both my power meter (Quarq) and without it. I've found that at lower speeds it seems much more accurate..when I really crank up it (speed), Strava underestimates my power pretty significantly...

400ft over 70miles!!!!!!!!!!! I don't get less than 4000 ft climbing on my 50 mile rides!

Honestly, the couple of times that I have ridden without a power meter I have found Strava's estimates to be sort of comical. I can only dream of being as powerful as they think I am. :D

I hate to say it but if you want to know what your power numbers are there is only one way to do it. Ride with a power meter.

For those of us who live in pancake flat areas (I can ride a century with < 200 ft of climbing), it seems to at least be in the general ballpark.

This. Strava thinks my 5 minute power is 786 watts. If my 5 minute power was 786 watts, I'd be the first 53 year old to win the Tour de France.

Strava power numbers are a joke. It's a stupid feature.

Also, just because someone else, or even a few people ascend at a similar power output, does not mean that you are putting out similar power output while ascending at the same speed. Comparing is stupid.

Darn, now I want a power meter.