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Power Models  :  Power Components Calculator
Temperature (Deg C)
Ride Distance (KM)
Relative Humidity (%)
Average Grade (%)
CRR (Rolling Resistance)
Wind Speed KPH
The Rider & Bike
Rider+Bike Weight (Kilos)
Ride Time (Mins:Seconds)
Initial Speed (KPH)
700 x 20
700 x 22
700 x 23
700 x 25
700 x 28
Final Speed (KPH)
Aero Bars (Typical)
Aero Bars Optimised (Typical)
Est: Height-Weight (RoadBike)
Est: Height-Weight (TTBike)
Est: Height-Weight (TriBike)
Pro Rider (RoadBike)
Pro Rider (TTBike)
Total Power Demands
Total Watts at Hub [PowerTap]
Drivetrain Efficiency (95-100%)
Total Watts at Crank [SRM]
The power components calculator implements a physical model of cycling power demands given parameters describing the cycling environment, rider and bike, returning the total power required to travel at the specified speed as well as components of power consumed by:
Elevation Change (Climb or Descent)
In other words this model reveals just where a riders total effort is going, with great insight into the proportions of power attributed to different factors, in a way that may motivate training attention to some of the inputs more than others (for example drag minimisation instead of power maximisation, etc).
Inputs: Environmental Variables
Temprature (Deg C). Input a temperature in degrees Celcius (e.g. 20)
Pressure (Millibars). Input the ambient air pressure in Millibars (e.g. 1013). You can get this number from any good weather forecast.
Relative Humidity (%). Input the ambient air humidity in percent (e.g. 20). Again you can get this number from a weather forecast.
Wind Direction. Select the applicable wind direction as a heading (e.g. NW) or else input a wind bearing between 0 and 255 degrees. This is the direction the wind is blowing from, not to.
Wind Speed (KPH). Input the wind speed in Kilometes per hour (e.g. 5).
Inputs: The Course
Ride Direction. Select the applicable direction as heading (e.g. NW) or else input a bearing between 0 and 255 degrees. This relates the riders direction to the wind, so a ride direction of "S" (180 degrees) is an unmitigated headwind when the wind direction is "N" (0 degrees).
Ride Distance (KM). Input the ride distance in kilometres (e.g. 40).
Average Grade (%). Input a gradient in percent (e.g. 3 is 3 percent, -2 is -3 percent).
CRR (Rolling Resistance). Select the coefficient of rolling resistance applicable to the course. The dropdown is a handy way to select typical values.
Inputs: The Rider & Bike
Rider + Bike Weight (Kilos). Input total weight in kilos (e.g. 80).
CdA. This is the metric of aerodynamic drag (
rag x frontal
rea) applicable to the rider and bike combined. The figure is expressed in metres squared. Typical cycling values are in the range .20 to .30
Tyre Radius. Input the radius of your wheels (including tyres) or simply use the dropdown to select one of the popular values.
Wheel Intertia. This is a hard to measure coefficient. It is suggested to retain the default of 12.
Inputs: The Ride
Ride Time (Mins:Seconds). This model is going to calculate power requirements for a given course of a given distance, hence the ride time is an important parameter which defines the average speed. Input values for minutes and seconds.
Initial And Final Speed (KPH). In spite of the Ride Time parameter this model also requires inputs for initial and final speed to accurately calculate power requirement attributed to acelleration or event decelleration. (e.g. 0 and 40).
Quote Power At / Drivetrain Efficiency
Power meters such as the SRM, Quarq & Ergomo measure wattage at the cranks. The actual wattage delivered to the hub, where a PowerTap would measure it, is a little bit lower due to drivetrain inefficiencies. Specify drivetrain efficiency in percent (eg 97.5, which would be a good estimate). The significance of this parameter is that, if the model is set up to calculate the power required to achive a particular time on a particular course, the power required of the cyclist will be a little higher if quoted at the crank. ie 97.5 watts required at the road = 97.5 watts at the at the hub = 100 watts at the crank, when drivetrain efficiency is 97.5%.
Outputs: Power Demands in Watts
The outputs illustrate the components of power consumed by each respective physical factor as well as total power requirements for the ride in question.