Stationary Bike Calculator
Indoor miles count differently: no wind, no hills, and a console that speaks its own language. This page converts time, speed and distance for stationary bikes — and translates erg pace into watts with the maker’s published formula.
- Distance, time and speed solver
- Erg pace ⇄ watts converter
- Free — no sign-up
Your indoor ride
Use the speed your console shows. Indoor distance is only ever as honest as that number — see the note below.
Your results
Distance
—
| Distance | — |
|---|---|
| Time | — |
| Speed | — |
On the console’s own scale. Compare sessions on the same bike, not across brands.
Erg pace ⇄ watts converter
—
Applies the erg maker’s published cubic: watts = 2.80 × (500 ÷ split)³. Fan bikes follow the same cubic shape with their own calibration.
Erg pace and watts table
The cubic law is unforgiving: from a 2:30 split to a 2:00 split is a 25% faster pace but nearly double the watts. That is why erg sessions are paced by power, not by chasing the speed readout.
| Split /1000 m | Erg speed | Watts |
|---|---|---|
| 1:30 | 40.0 km/h | 480 W |
| 1:40 | 36.0 km/h | 350 W |
| 1:50 | 32.7 km/h | 263 W |
| 2:00 | 30.0 km/h | 203 W |
| 2:10 | 27.7 km/h | 159 W |
| 2:20 | 25.7 km/h | 128 W |
| 2:30 | 24.0 km/h | 104 W |
| 2:40 | 22.5 km/h | 85 W |
| 2:50 | 21.2 km/h | 71 W |
| 3:00 | 20.0 km/h | 60 W |
How indoor distance works
The arithmetic is the same as the road — the homepage solver uses the identical relationship — but the meaning of “speed” changes. Outdoors, speed is measured over the ground. Indoors, the console derives it from flywheel revolutions against a wheel size the manufacturer chose, and on many bikes the resistance setting does not change the reading at all. Treat indoor distance as a consistent training log on one bike rather than a claim about the road. For outdoor power and speed, the watts to speed calculator uses the full drag model instead.
A note on fan bikes: air-resistance bikes have no fixed speed scale at all — the harder you pedal, the faster the fan spins, following the same cubic law as the erg table above. On a fan bike, work in watts or calories per minute and ignore any distance readout beyond comparing your own sessions.
A 45-minute session at a console speed of 28 km/h: 28 × 0.75 h = 21.0 km (13.0 miles), at a pace of 2:09 per km. On the erg, holding a 2:00 split for the same session means 203 W — a very different, and much more honest, description of the work.
Limitations
- Console speed is the manufacturer’s estimate; two brands at “28 km/h” can be meaningfully different efforts.
- The erg cubic is the published relationship for flywheel ergs. Magnetic-resistance bikes do not follow it.
- Indoor distance has no wind, gradient or coasting in it — never compare it directly with a road ride.
Frequently asked questions
How far do I ride in 45 minutes at 28 km/h?
Distance is speed × time: 28 km/h for 0.75 hours is 21.0 km. The solver above runs it in any direction — fix any two of distance, time and speed and it finds the third.
Why does my stationary bike’s distance look wrong?
Most indoor bikes estimate distance from flywheel speed using a fixed wheel size the maker chose, and resistance level rarely changes it. Two bikes at the same displayed speed can mean quite different efforts — which is why this page treats the displayed speed as its own scale and converts honestly within it.
What does the erg pace-to-watts table describe?
Air-bike and bike-erg machines whose resistance comes from a fan or flywheel follow a cubic law: double the pace takes roughly eight times the power. The erg maker publishes the exact relationship — watts = 2.80 × (500 ÷ split)³ for a split per 1000 m — and the converter and table on this page apply it directly.
Is erg speed the same as road speed?
No. The erg’s km/h is distance on its own flywheel scale — 30 km/h on the erg is simply a 2:00 split per 1000 m. It does not include wind, hills or your position, so it will not match the road; the watts are the honest number to compare.
Can I use this for a spin bike without a display?
Only if something gives you a speed or a distance — a cheap bike computer with its sensor on the flywheel, or the class app’s estimate. With time alone there is nothing to convert; ride to effort and log the minutes.
Keep working the numbers
Indoor numbers translate back to the road with care. The bike speed calculator handles the same distance-time maths outdoors; the watts to speed calculator shows what your erg watts would do against real air; the gear speed calculator covers the geared side of riding; the triathlon pace calculator plans the race the winter training is for; and the bike pace chart prints the conversions.
Bike Speed Calculator
Any two of speed, pace, distance and time — get the other two.
Open the calculator →Watts to Speed Calculator
The power a speed takes — and the speed a power buys.
Open the calculator →Gear Speed Calculator
Speed from chainring, cog, wheel size and cadence.
Open the calculator →Bike Pace Chart
Every speed from 10–50 km/h with mph and pace — printable.
Open the calculator →- Concept2 — pace and watts relationship — the published cubic behind the erg converter and table