Bicycle Gear Calculator: Speed, Cadence & Power

Understanding Cycling Cadence

Cadence is the number of revolutions of the crank each minute, measured in revolutions per minute (rpm). It tells you how quickly you are turning the pedals, not how fast the bicycle is travelling.

Modern cycle computers, including Garmin and Wahoo devices, can display cadence when connected to a compatible cadence sensor or power meter. Many smart trainers can measure it too. A GPS cycle computer does not necessarily measure cadence by itself.

There is no single ideal cadence for everyone. A range of roughly 60 to 100 rpm is common for recreational cycling, but what feels efficient and comfortable depends on your fitness, effort and terrain. In the same gear and at the same power, a slower cadence requires more force on each pedal stroke; a faster cadence reduces that force but can increase the effort of spinning your legs.

Experiment to find a cadence you can sustain, especially on hills. Use these gearing calculations to see which chainring and sprocket combinations let you stay near your preferred cadence at different road speeds. The Virtual Ride & Gear Adviser can also suggest a suitable gear for a chosen power and gradient.

Further reading: Bicycle cadence on Wikipedia.

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Gear calculation

Use this website to choose the ideal gearing for your personal riding style.

• At the high speed end, how fast do you want to be able to go with a cadence near your maximum? Can you produce enough power to achieve this speed, on the flat, uphill/downhill, and with a headwind / tailwind?
• At cadences lower than 60 rpm it is harder work to create a given amount of power. Sure, athletes can create high power at low revs but it is still less efficient than pedalling faster! So, at the low end do you have a suitable gear that you can pedal within your cadence range that will get you up a steep hill?
• In between, have you enough gears to be able to pedal at all speeds and keep within your target cadence range. It is inefficient if when you reach your max cadence in one gear the change to the next gear takes you below your min cadence.

Click on View analysis and information is provided for that gear set and for your personal information:

• For that gear set what gradient of hill you can climb given your preferred cadence, weight and power capabilities.
• What power is required to pedal at different speeds in different gears with and without a headwind.
• For each gear ratio; what speed could you achieve within your cadence range and how many gear inches does the gear equate to.
• For each MPH point - which gear combinations could you use at this MPH and remain within cadence range

Change your gearing and see what the effect is.

Gear calculation input data

A figure of two watts (of power) per Kg of body weight is often quoted as a maximum sustainable power for a fit person. Athletes can produce figures much higher than this.

The calculations take frictional losses (tyres, bearings, chain), air drag and energy to climb a gradient into account when calculating power requirements.

The calculations for air resistance with a headwind / tailwind (enter a negative headwind) assume the wind is not at an angle and not affected by objects such as buildings or hedges.

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K_A and C_R

K_A is a coefficient used in the formula that calculates air resistance:

Source Bicycling Science:

0.368 Roadster, Utility bicycle
0.245 Sports bicycle
0.182 Road racing bicycle

Another source gives:
0.17 for a rider tucked into an aero position.

K_A varies from 0.1 to 0.4.

C_R is a coefficient used in the formula that calculates rolling resistance:

Source Bicycling Science:

0.008 Roadster, Utility bicycle
0.0053 Default quoted by many authorities.
0.004 Sports bicycle
0.003 Road racing bicycle

C_R varies from 0.0025 to 0.008.

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