Secret Formula for Speed on a Bike (against power)

Aeroweenie.com has posted a large dataset of rider speed vs rider power (see here). From this it is fairly easy to plot speed vs power and excel will even give you the formula

Here it is

Rider Speed in KPH = 14.67 Ln(watts) - 42.4

So now, assuming average weight, CDA, temperature etc you can easily calculate your predicted speed!

ps.
If you know a lot more variables then more accurate speed prediction calculators are available! http://www.aeroweenie.com/calc.html