Speed on zwift way higher than irl

Hi, I have been using zwift for a year and I have noticed that my avg speed is much higher than irl, and I’m not talking about 1,2 kph, but even 5-7, I’m 15 y/o ,4.6 w/kg ftp ,55kg, I’m using well calibrated favero assioma uno power meter pedals, so I can’t imgaine my power readings are not accurate. Can someone explain why such thing is happening? Is it that, zwift pays too much attention to w/kg instead of raw wattage? Does anyone have anything similar?

Ps. I checked on power to speed site and those numbers were just like I got while riding outside, so inacurrate power readings can’t be an option.

Hi Andrzej, I see that you are a lightweight rider. If you are also “short” in stature this could be one of the reasons your Zwift speeds are anomolously high compared to IRL

The Zwift speed algorithms seem to be quite unrealistic for people of low weight plus low height.

This is one (possibly contentious) reason for your observation. On the plus side, you should do quite well in Zwift races.


Yes, I’m rather short even compared to my age, so thats probably the reason. Thanks for the very fast feedback :smiley:

Almost certainly your short height, but your FTP is already quite nice. :+1:

I’m a little bit heavier than you and before my crash the Zwift speeds for me (at 175cm high) when riding on my own and compared to real life were fairly similar.

One area where the Zwift average goes higher is that you never brake for corners, even downhill hairpins you just fly through them.

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Hi @Andrzej_Kobak

Welcome to the forum.

On Zwift you have a really good bike and nice smooth roads and perfect draft.

Also lighter riders has a bit of a advantage. :face_with_hand_over_mouth:(Just teasing a little)


Yes, it looks like the height is the main thing, I’m 166/167 cm tall and actually 51/52 kg because I made mistake writing this post so that as well can make a difference.

are you comparing speeds riding solo or in a group on zwift to solo vs group IRL?

Speed solo on zwift while riding in open world for instance watopia compared to irl

I find that my speed riding through a volcano IRL is also very different. 193cm, 91kg.


5-7 kmh faster than outdoors sounds about right for me (72kg, 170cm). It only takes about 135-140w to do 32 kmh without drafting… I wish! More like 185-200 outside. You also have no wind, perfect pavement, ultra-aero riding position, and (probably) a superbike or Tron on Zwift.

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For me it was similar in Zwift, my IRL bike is the S5 2020 (on DT Swiss wheels), 54cm frame and my position on it was very aero.

It’s when you add draft in Zwift that the speeds escalate.

My other IRL bike is a featherweight UCI-illegal Canyon Ultimate CF Evo, it is also similarly fast.

After posting that I remembered that my IRL bike is in Zwift (CAAD 9 with HED Jet RC6… close enough to CAAD 12 with HED Vanquish RC6) and I use it for fun sometimes in the game. Slower but not too far off from the Tron - ~140w for 20 mph without drafting. Would be nice :grin:.

You also don’t have to slow down to avoid other riders, or going around sharp corners. This is probably the most significant reason for the speed disparity between Zwift and IRL.

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This big problem is, imo, in the descents or ridding with big groups.

Yesterday I did a Cat C group ride and the speeds in the flat were between 42-46 km/h.
At that pace it´s easy to loose the draft …