Cycling calculators
Ten small tools I built because I needed them myself. Everything runs in your browser — nothing is sent anywhere, nothing is stored, no sign-up. Change a number and the answer changes. The four that people search for have a page of their own, with the background explained; the rest are right here on this one.
The big four — each on its own page
FTP from a test
Ramp, 20-minute or 8-minute test in, FTP and your zones out — plus what each test flatters, what it punishes, and how often to re-test.
Power zones
All seven zones in watts from one number, with what each zone is actually for and where sweet spot sits between them.
Watts per kilogram
Your W/kg, what +10 W or −5 kg would do to it, and how many kilograms a target really costs. Plus which of the two is faster to move.
Climb time and speed
Time, speed and VAM for any climb, and how fast a given number of watts makes you go on the flat. With an honest note on why reality is slower.
And four more, right here
TSS and intensity
How much training stress was that ride?
One hour at exactly FTP equals 100 TSS and an intensity factor of 1.0. This is what lets an easy two-hour ride and a short brutal session sit on the same scale.
Ride fuelling
How many carbohydrates and how much fluid does this ride need?
Work in kilojoules is close enough to calories burned for practical purposes, because a cyclist is roughly 22–25% efficient and the two errors cancel. Carbohydrate figures are the widely used general range, not personal advice — and if you eat low-carb, they do not apply to you.
Heart rate zones
What are my heart rate training zones?
Threshold heart rate gives better zones than max HR, and you get it from the same 20-minute test: the average heart rate of the last 20 minutes. Heart rate lags power by a minute or two, so on short intervals trust the watts.
Gearing and cadence
What speed does this gear give me at this cadence?
2105 mm is a 700×25c tyre; 2136 mm is a 28c. Useful for one question above all: is your easiest gear low enough to hold 70 rpm on a 10% ramp?
Why these ten?
Because these are the questions I actually had to answer to run a 16-week plan around shift work: what my zones are, what a test result means, how much stress a session cost, and whether the gearing on my bike is low enough for the climbs I keep avoiding.
Everything here is standard cycling arithmetic, not a secret. The speed and climb tools use a simple physical model — rolling resistance, air drag, gravity — so they are optimistic on a real road with real wind. The fuelling numbers are general ranges, not advice for any particular person.
Found a mistake in one of these? Tell me — I would rather fix it than leave it wrong.