One question, answered well: how many watts does a ride take, and how fast will your watts carry you? The rest of the site exists to support that answer.
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At the center is the cycling watts calculator, which models the four forces every rider pays for: gravity, air drag, tire rolling resistance and drivetrain loss. Around it sit calculators for the questions that come before and after it: how strong you are, how heavy you are, how steep the road is and how much training a ride adds.
Everything here is about cycling power, speed, climbing and training load, so each topic gets a full page instead of a thin one.
The physics tools, including the speed, hill climb, CdA, aero watts and rolling resistance calculators, all share one power model, so a result on one page agrees with the others. The CdA calculator solves that same model in reverse.
The performance tools, namely FTP, power zones, critical power, TSS, W/kg and VAM, each use their own published convention, such as Andrew Coggan's training-load work or the Monod & Scherrer critical power model. Each is the right model for its job rather than one formula stretched over everything.
Every formula and default constant is written down with its source and assumptions before it is built into a calculator. The methodology page shows how, the sources page lists every citation, and the editorial policy covers corrections. Where a number rests on an assumption, such as air density, tire rolling resistance or drivetrain efficiency, we state it instead of presenting it as exact. Nothing is invented to fill a gap, and worked examples on each page are computed by the same code the calculator runs, so they cannot drift from what you see.
Every result here is an estimate for training and planning, not a laboratory measurement. Equipment, road surface, wind, rider position and day-to-day physiology all move real power output. Use the numbers to compare scenarios consistently, and lean on a calibrated power meter when you need to know what actually happened.
This site is built and maintained by a recreational cyclist. I am not a coach, a sports scientist or a doctor, and nothing here replaces one. There is no company or sponsor behind it, and no product to sell you.
What I do is read the published models carefully, write each one down on the methodology page with its assumptions, check every calculator against worked examples done by hand, and say plainly where a number is an estimate. Each page shows the date its content last changed. If you find a mistake, or a result that does not match your own power meter, please get in touch and I will look into it.
The calculators estimate power, speed and training load. They do not give medical or health advice, so talk to a doctor before changing your training if you have a health concern.
