Cycling Calculators

Spokiva is a set of free cycling calculators built on one idea: the number you get back should come from the physics, not from a rule of thumb. Every tool here runs entirely in your browser, updates the moment you change an input, and never asks you to create an account. Whether you are sanity-checking a VO2 max estimate, converting watts into speed for a flat road time trial, or working out whether a 34/32 bottom gear will actually get you up next weekend’s climb, the answer takes seconds.

Most riders end up guessing at these numbers, or trusting a training app that hides its assumptions. The Spokiva cycling calculators do the opposite: they show you the breakdown. When you convert power to speed you can see how many watts went to air, to rolling resistance and to gravity. When you estimate VO2 max you can see which protocol produced the figure. That transparency is what makes the results useful for making decisions rather than just for curiosity.

What each calculator does

VO2 max calculator

VO2 max is the maximum volume of oxygen your body can use per minute, expressed in millilitres per kilogram of body weight per minute. It is the single best-known marker of aerobic capacity, and it matters as much to runners as to cyclists. TheVO2 max calculator estimates it two ways: from your cycling FTP using the ACSM equation, or from your resting and maximum heart rate using the Uth–Sørensen ratio. It returns your relative and absolute VO2 max, your aerobic capacity in METs, and an age-graded fitness rating, alongside a fullVO2 max chart so you can see where you sit against the population norms for your age and sex. If you would rather test by running, the page also explains theCooper 12 minute run protocol and the arithmetic that turns the distance you cover into a VO2 max score.

Power to speed calculator

The cycling power to speed calculator answers the question every rider with a power meter eventually asks: what is this effort actually worth? Enter your watts, your combined rider and bike weight, the gradient and your riding position, and it returns your predicted speed plus a watt-by-watt breakdown of where the power goes. On a flat road above roughly 25 km/h, aerodynamic drag dominates everything else, which is why position and CdA change the answer more than fitness does. Point the same bike power to speed calculator at a 7% gradient and the picture inverts completely: weight becomes the number that decides your speed.

Speed to power calculator

The speed to power calculator runs the same model backwards. Name the speed you want to hold and it tells you the wattage that takes, which makes it the right tool for pacing. Before a time trial, enter the average speed that gets you to the finish inside your target time and compare the required power against your FTP. If the calculator says 290 watts and your threshold is 250, you have learned something valuable before the start ramp rather than three kilometres from the finish.

Gearing calculator

The bicycle gearing calculator turns a chainring, a sprocket, a wheel size and a cadence into the four numbers that describe a gear: ratio, gear inches, development and gain ratio. Use it to check that a new cassette really gives you the climbing gear you think it does, to compare a 1x setup against a 2x, or to see what cadence a given gear demands at your target speed. Because the maths of a chain drive is the same everywhere, it also works as amotorcycle gearing calculator for final drive: enter the front sprocket as the chainring and the rear sprocket as the sprocket.

How to get a trustworthy answer

1. Weigh everything. Total weight means rider, bike, kit, bottles, tools and food. Two full bottles and a saddle bag are easily 2 kg, and on a climb that is worth real time.
2. Be honest about position. Choosing “time trial” when you spend the ride on the hoods will overstate your speed by several km/h. Pick the position you will actually hold for the whole effort.
3. Match the surface. Rolling resistance on fresh tarmac, worn tarmac and gravel differ by a factor of two or more. The surface setting is not decoration.
4. Use the same method every time. This matters most for VO2 max. Field estimates carry a margin of error, but that error is consistent, so the trend across months is meaningful even when the absolute value is approximate.

The models behind the numbers

The power and speed tools use the standard cycling power equation, the same one behind the published models used in coaching and in aerodynamic testing. Total power is the sum of four terms: aerodynamic drag, which scales with air density, CdA and the cube of speed; rolling resistance, which scales with the coefficient of rolling resistance and total weight; the gravitational term on a gradient; and drivetrain loss, typically two to three percent through a clean chain. Solving that equation for speed is what the power to speed calculator does, and solving it for power is what the speed to power calculator does.

The VO2 max estimates come from two peer-reviewed protocols rather than a proprietary formula. The cycling method uses the American College of Sports Medicine cycling equation, applied to the maximal aerobic power implied by your FTP. The heart rate method uses the Uth–Sørensen–Overgaard–Pedersen ratio, which relates VO2 max to the ratio of maximum to resting heart rate. Both are field estimates and neither replaces laboratory VO2 max testing, where expired gases are measured directly — but both are good enough to benchmark yourself and to track change over a season.

Built for the way riders actually work

Every calculator toggles between metric and imperial, so kilograms and km/h or pounds and mph are equally at home, and switching units never makes you retype an input. The pages are fast and fully responsive, so they work on a phone at the roadside as well as on a laptop while you plan a season. Nothing you enter leaves your device: the calculations happen locally, there is no account to create, and there is no data to harvest. Pick a calculator above and start with your own numbers.