Well, distance = average cadence x minutes x wheel diameter (2.105m for 700x25c tyres). If you have a speed sensor on your bike, your head unit should come up with a figure without you having to do the math.

I track indoor distance from the perspective of component wear rather than training benefit. As long as it is ballpark, I'm not too concerned about absolute precision.

Reality is that it is not easily comparable.
If you use training peaks consider tracking tss instead, rather than pure km.
I always use the rough equation in my head that indoor training probably gives about 120% of the relative load I would have from the same time spent outdoors training, mainly due to there not being any stop start etc etc.

Since you have only cadence and HR available, you don't have much to work with for an accurate figure unless you always stay in the same gear. If you do you can use average cadence to calculate average wheel speed and just multiply by the duration.
However, all that does is give you a number. It's meaningless from very perspective.
Better to do an guesstimation based on average HR and duration with comparison to outdoor rides with similar figures.

My advice, would be to just switch to measuring time on the bike and forget kilometers. At least that way you're recording a real quantity. If you really want a distance figure you use the above methods, or just multiply the time by a typical average speed number (it'll probably be about as accurate as the above methods), but record the time. Recording distance as a training metric just provides an incentive for you to do easier routes outdoors, or lower resistance indoors. Neither of these is a good idea as a general rule.

"forget kilometres"


but, but but ... that would be LOGICAL!

(thanks all)

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"Find a way, not an excuse". Goony, Kona, 2009

If you ride 20 mph outside for an hour and get really sweaty and then ride inside for an hour and get really sweaty, I’d go with 20 miles for your workout.

Although if you don't use a fan inside, sweaty could be just 10-15miles!
But yeah, I agree. If it feels fairly similar effort, assume similar speed.

This is probably going to get shutdown by everyone saying just go by time or TSS but... if you are just looking for a rough idea of how many km you are doing (ie. for your own satisfaction), I'd say just take the average speed of your last year of outdoor rides and multiply it by your time riding inside. Like if you typically go about 30 km/hr and ride for an hour, I'd say you'd probably be pretty close to 30km.

Then again, time spent riding is probably more useful anyways... its like comparing a 5 hour road ride on a TT bike to a 5 hour mountain bike ride - you still spent 5 hours riding (and accumulated 5 hours of training stress!) but probably covered vastly different distances.

I'm in a similar situation with no instrumentation at all on my indoor setup. Outdoors I average about 17 mph so if I want to know my distance indoors I just conservatively take my time and multiply it by 15 mph.

Alternatively, I know OP said no spare cash but Cateye makes some nice cheap little bike computers, you can get one with just basic speed/distance/cadence for around US$50:

https://www.cateye.com/.../products/computers/

I velcro’d a Garmin speed sensor to the wheel of my dumb trainer, for speed and distance. Works great. I’m very old school, and train by feel. Never been interested in power or whatever else is trending today. Getting speed and distance on my dumb trainer isn’t so much about comparing to outside riding, as it is about having something I can compare to each day, with how my muscles are feeling. I just went over 30k miles on the dumb trainer, since adding the sensor, and it’s worked well for me.

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Athlinks / Strava

Depends how you ride, i guess. I dont really look at the speed distance, But i’m using a smart trainer. Just trying to get the workouts done, But middle cog on a 12-25 cassette and small chainring gives me about 24kph with a cadence of around 90, so way slower than I would go on the road for the same power. I guess switching off erg mode, would Force me to change gears and get more of an estimate of the speed and distance, aside from strava/garmin challenges, I just dont see the point

Well you wouldn’t go as far in an one hour ride if it was all climbing, versus flat, so I would focus on intensity for your conversion. So suppose you are doing a 1hour workout with 2x20 on the trainer at 150 bpm (or whatever your intensity measure is). How fast would you be going outside at that pace/intensity? If it is 22 mph, then your interval mileage is 0.66*22. Toss in some reasonable number of miles for the other 20 minutes (how about 5 miles for the low intensity cool-down part).

What kind of KM... flat, windy, gravel, in aero position etc...


The real comparison is to look at everything (indoor and outdoor) in TSS, and even then 2hrs @ 200 watts in ERG mode are A LOT harder than the equivalent outside.


KM are only useful if you want to make conversation with your non cyclist friend

Depends on the outside. If the terrain dictates over/under, the TSS for 200w per hour doing that is higher than 200w steady. I can’t ride these hills by my hood in a 39/30 or TT bike 54/28 at just Z2.

200w AP on rolling terrain is a lot tougher than 200w dead steady erg.

For the same IF / TSS... on my trainer, ERG is a lot harder (constant tension, no micro brakes)

Two thoughts:

1. Use perceived effort, i.e. how far would you go in your typical 1hr ride at that PE. Pro riders used to use this and then add ~30% to the distance; due to the lack of stop signs/lights, corners, downhills, etc. (trainers are more time efficient).

2. Use Zwift. If you have a speed sensor that can transmit in bluetooth than you can tell Zwift which dumb trainer you have and it will know the speed vs. watts load curve. Then you can see your KMs on Zwift. You just need a laptop (or even a phone) and wifi.

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ECMGN Therapy Silicon Valley:
Depression, Neurocognitive problems, Dementias (Testing and Evaluation), Trauma and PTSD, Traumatic Brain Injury (TBI)

Firstly, hope all is well over there in Melbourne - I worked there for 6 months a few years ago, great place.

I have a really old wind trainer work-out book (I got given a copy about 25 years ago when I was doing TT's in the UK) and it suggested that time on a wind trainer was worth 2-3 x time on the road due to things like lack of tailwinds, stopping at junctions, downhills etc etc.

I guess it depends on the session you're doing and whether you're on a fancy smart trainer or not..?

Many thanks QW for your most kind thoughts. We are doing it tough in the great city of Melbourne, but it's day-by-day and we'll get there, wherever "there" is.
And thanks heaps for your advice. This has been a most worthwhile thread.

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"Find a way, not an excuse". Goony, Kona, 2009

Then that means the person isn't well focused riding outdoors.

One has to learn how to make routes and have the riding skills to keep producing power down hills, around corners, etc.....

If I live "in town" with tons of hills and turns and can keep my ride time and total time within 3min of each other for an hour ride.....and manage roughly identical KJ/hr to an indoor ride..........so can you.

Also, 2-3x? That's bogus. Lack of tailwinds? Uhmmm, when was a tailwind time to lolly gag and be lazy? Maybe 2-3x if you live in inner city London or NYC and have to make it out of town.

Time is time, KJ's are KJ's. Mileage is just a consequence of the inputs.

Your body knows time and effort not km's.

I know that doesn't help. What I would do if it were me, I'd look at my last 30-40 rides add up the time and distance then figure out the average kmh. I'd assign that figure to my indoor workouts

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

one (of probably many) things to consider when trying to convert from trainer to out doors is the fact that outdoors it is hard to be pedalling 100% of the time (coasting, stopping, etc) whereas on the trainer you do tend to pedal 100% of the time. I have seen some places where it was suggested 45 min trainer time is equivalent to 1 hour road time.... Certainly there are a lot of differences but I think to try to equate them is not all that easy both effort wise/ definitely speed distance wise etc.

Indeed. I would point out that the book in question was written some time ago, and somewhat before even heart rate monitors were widely available and affordable. I guess now that effort (HR/Power/Whatever) is measurable and more affordable for most folk it is way easier to compare inside and outside.

I personally do find it way harder to focus on quality riding outside (especially in a group ride, but then that's a different kind of training session) (and we don't draft in tri's), hence I use a wind trainer for quality sessions. I do certainly admire those folk who are able to train so efficiently outside.

Has everyone has said it is very difficult to relate indoor riding distance to outdoor distance.

I have a old school trainer like you and here is what I have come up to try and get a rough approximation. I have 100's of outdoor ride data to pick from and I have found that my heart rate for a outdoor ride on my road bike on flat ground is extremely consistent. For me I have made a chart.

Average heart rate 120's- 16 mph
Average heart rate 130's- 17 mph
Average heart rate 140's- 18 mph
Average heart rate 150's- 19 mph
Average heart rate 160's- 20 mph
Average heart rate 170's- 21 mph
Average heart rate 180's- 22 mph
My max is 200 bpm

Sorry am in the US so still use old fashion mph instead of KM.

Obviously lots of climbing, heat, or very windy conditions can skew these numbers and it is not accurate at all for my time trial bike, mountain bike, or cyclecross riding but I have found that over the years those numbers are remarkably accurate. At the end of the year before starting winter training I do at least a couple of rides in each of those zones to confirm the numbers and they have stayed stable over the years.

If you have enough training data just an idea for you to try.