Cycling Power Zones & W/kg Calculator
Work out your FTP from a test, your watts per kilogram and Coggan’s seven power zones, then see how fast that power takes you on the flat or up a climb.
How to Use
- Pick a mode: FTP & zones, Speed on the flat, Climb or VAM from a ride.
- For zones, choose the test you did — 20 minutes, two 8-minute efforts, a ramp test or a known FTP — and enter its power in watts, plus your weight for W/kg (kg, lb or stone).
- For speed, enter your power, your weight and the bike’s. CdA (your frontal drag area), Crr (tyre rolling resistance), air density and drivetrain efficiency start at typical values you can change.
- For a climb add the gradient and, if you like, its length to get the time; for VAM enter the height you gained and how long it took.
- Read the readouts and the zone table or chart, and open Show Work for every step, including the force balance behind the speed.
Worked Example
FTP and zones from a 20-minute test. A 70 kg rider averages 250 W for 20 minutes. FTP = 250 × 0.95 = 237.5 W, or 237.5 ÷ 70 = 3.39 W/kg. Zone 2 is 56–75 % of that, 133–178 W; zone 4 is 91–105 %, 216–249 W.
Speed on a climb. The same kind of rider, 70 kg on an 8 kg bike, holds 250 W up a 7 % road. With 97 % of the power reaching the wheel, gravity (53.4 N), rolling (3.8 N) and air (3.2 N) balance at 14.5 km/h, which climbs 4.016 × sin 4.00° × 3,600 = 1,009 m per hour; 10 km takes 41:30.
The common mistake: using the 20-minute power as FTP. Setting zones from 250 W instead of 237.5 W pushes everything 5 % too high: the top of zone 2 becomes 187.5 W instead of 178 W, and threshold work tops out at 262.5 W instead of 249 W — efforts most riders can’t hold for the intended time.
Show Work
Formulas
Where Power Zones Come From
Andrew Coggan, an exercise physiologist, and coach Hunter Allen set out the seven training levels in their book Training and Racing with a Power Meter. They anchored the zones to functional threshold power — the highest power a rider can hold for about an hour — because, as Coggan explains in his TrainingPeaks article on power training levels, power at lactate threshold is the most important physiological determinant of endurance cycling performance, so it makes more sense to set zones from it than from power at VO₂ max. The same table gives approximate heart-rate bands as a percentage of threshold heart rate and effort on Borg’s 10-point scale.
Testing for a full hour is hard, so the usual field test is a 20-minute all-out effort with 5 % taken off, as TrainingPeaks’ threshold-test guide describes. Its coaches also point out the limits: the 95 % rule fits roughly half to 60 % of riders, and one coach reports FTP from 86 % of 20-minute power for a track sprinter to 96 % for some time-triallists. Ramp tests, popular on indoor trainers, are scored from the best minute instead, most often at 75 %.
VAM, from the Italian velocità ascensionale media (average ascent speed), measures climbing in metres gained per hour, which lets riders compare efforts on climbs of different length and steepness.
About This Tool
This calculator puts the common power numbers in one place: FTP from the test you actually did, watts per kilogram with weight in kg, lb or stone, the seven Coggan zones with heart-rate guides, the speed a power gives you on the flat or a climb from the physics of rolling resistance, gravity and air drag, and VAM from a climb you rode. The speed model assumes a steady effort, still air and the CdA, Crr and air density you give it — change them to match your position, tyres and altitude; they are typical values, not measurements of you.
Everything runs in your browser; nothing you enter is sent anywhere. For general information only — not medical advice. Talk to a doctor or other qualified professional about your own health.
Related tools: Target Heart Rate Zones, Rowing Split & Watts Calculator, and Swimming Pace Calculator.
Frequently Asked Questions
How do I calculate my FTP from a 20-minute test?
Take your average power for the 20 minutes and subtract 5 %: 250 W × 0.95 = 237.5 W. TrainingPeaks also lists two 8-minute tests (best × 0.90) and a 30-minute test used as it is. A ramp test is commonly scored as 75 % of the best 1-minute power, so 320 W gives 240 W.
What are the seven Coggan power zones?
As a percentage of FTP: 1 active recovery up to 55 %, 2 endurance 56–75 %, 3 tempo 76–90 %, 4 lactate threshold 91–105 %, 5 VO₂ max 106–120 %, 6 anaerobic capacity above 121 %, and 7 neuromuscular power for maximal sprints. With a 237.5 W FTP zone 2 is 133–178 W.
How do I work out watts per kilogram?
Divide your power by your body weight in kilograms. A 237.5 W FTP at 70 kg is 237.5 ÷ 70 = 3.39 W/kg. If you weigh yourself in pounds, divide by 2.2046 first: 154 lb is 69.9 kg.
How fast will I go at 200 watts?
On a flat road with no wind, a 75 kg rider on a 9 kg bike at 200 W does about 33.4 km/h with typical road values (CdA 0.32 m², Crr 0.005, air 1.225 kg/m³, 97 % drivetrain). Doubling to 400 W only reaches 43.2 km/h, because air drag rises with the square of speed and takes 80–87 % of the power.
What is VAM in cycling?
VAM (velocità ascensionale media) is the height you climb per hour. Gaining 800 m in 45 minutes is 800 ÷ 0.75 h = 1,067 m/h. At 250 W a 70 kg rider on an 8 kg bike climbs a 7 % slope at about 14.5 km/h, a VAM of 1,009 m/h.
How do I use the Cycling Power Zones & W/kg Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Setting training zones after a test
A 250 W 20-minute test gives a 237.5 W FTP, so threshold intervals in zone 4 sit at 216–249 W.
Comparing riders of different sizes
240 W at 75 kg is 3.20 W/kg; 237.5 W at 70 kg is 3.39 W/kg — the lighter rider is the stronger climber.
Working out what a position change is worth
At 200 W on the flat, cutting CdA from 0.32 to 0.25 m² lifts speed from 33.4 to 36.0 km/h; sitting up at 0.40 m² drops it to 31.1 km/h.
Pacing a climb
At 250 W, a 70 kg rider on an 8 kg bike takes about 41:30 for 10 km at 7 %; at 65 kg the same power gives 39:14.
Checking a ride file
800 m climbed in 45:00 is a VAM of 1,067 m/h; with 260 W at 68 kg that was 3.82 W/kg.
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