How does Cadence estimate power?

A power meter is the gold standard for training with power, and it’s also a few hundred dollars of hardware. If you don’t have one, Cadence can estimate your watts instead (an Elite subscription feature), so every power field on your screens works on any outdoor ride. Here’s how it works, and, just as important, what an estimate can and can’t do.

When Cadence estimates

The rule is simple: Cadence estimates power only when there’s no power meter added in Settings ▸ Sensors, on an outdoor ride. While it’s estimating, power fields show a small (⚡ EST) badge so you always know where the number comes from, and the ride’s Power section is tagged “Estimated” afterward.

Cadence will never guess on top of a real meter:

If you’ve added a meter but it hasn’t connected yet, your power fields say “Connecting…” and wait for it.
If your meter is connected and reads zero (coasting, soft-pedaling), that zero is real and stays. Estimation never fills it in.
Indoor rides aren’t estimated. The estimate needs your real speed and real hills to do its physics, and a trainer has neither, so indoors you’ll see “Est. Power: Outdoor.”
It’s cycling only (runs use different physiology), and it runs on your phone. A Watch Only ride doesn’t show estimated power while you ride, but Cadence estimates it when the ride comes into the app, as long as it’s an outdoor ride without power meter data. Older rides can be estimated from the ride’s edit screen with Process Estimated Power.

If you’re not on Elite yet
Cadence records estimated power on every qualifying ride whether or not you have an Elite subscription. You just can’t see it yet. That means the day you upgrade, your back catalog of rides already has power data on it, with no re-processing and nothing lost.

What if I switch power sources mid-ride?
If your power source changes during a ride — say you start on a bike without a power meter, then switch to your bike with one while paused — the ride ends up with some estimated watts and some measured ones. On rides recorded with Cadence 2.9.2 or later, Cadence saves that ride as a power meter ride: every watt it recorded is kept, including the estimated part, it isn’t tagged “Estimated,” and its watts are never recalculated when you edit it. Rides from earlier versions can’t tell the two apart, so they stay tagged “Estimated” and are recalculated as a whole when edited.

How the estimate works

Cadence works out, second by second, how many watts it must have taken to move you down the road, using the same forces a power meter feels through your pedals:

Your weight (you + your bike)
Your speed, and how quickly you’re speeding up. Accelerating hard costs real watts
The hills: climbing takes far more power than flat or downhill, and coasting down correctly reads zero
Air resistance: the biggest force at speed; depends on your Riding Position
The wind: when Cadence has weather data for your ride, pushing into a headwind costs extra watts, and a tailwind gives some back. Weather stations measure wind high above the ground, so Cadence counts roughly the strength you actually feel down at handlebar height. Note that wind accuracy can vary depending on the quality of the weather data, so like everything else here, it’s an estimate.
Rolling resistance: how much the road drags your tires; depends on your Road Surface

Cadence adds these forces up using a published road-cycling power model (Martin et al., 1998), a model sports scientists validated against real power meters. It’s also the same physics engine behind Cadence’s calorie estimates, so your bike’s settings shape your watts too. Riding Position, Road Surface, and E-Bike Compensation all live in Settings ▸ Gear ▸ (your bike). On an e-bike, Cadence shows your legs’ share of the work, not the motor’s.

Riding Position, Road Surface, and E-Bike Compensation all live in Settings ▸ Gear ▸ (your bike), and you can change them for a single ride in Edit Activity ▸ Bike Setup.

The honest part: it’s an estimate

Estimated power will not match a power meter, and it’s important to understand why. The estimate uses the local weather forecast for wind, not a wind sensor on your bike. It knows the general wind over your ride, but not the gust that just hit you, or the calm spot behind a hedge. It can’t see you drafting behind another rider. And second-by-second numbers are rougher than a meter’s, especially on short punchy efforts. If you pedal on descents, the estimate reads low there. When gravity alone explains your speed, Cadence can’t tell that you’re also pushing on the pedals.

Why power can spike as you crest a hill
The most common place to see a spike is right as you go over the top of a climb. Cadence sees your speed change straight away, but it reads hills from your altitude, and altitude readings trail the road by a few seconds. So as you tip over and start picking up speed, Cadence briefly thinks you’re still climbing, and it counts both the climb and the speed-up as effort from your legs, even if you’ve stopped pedaling. The same delay works the other way at the bottom of a hill, where power can read low for a few seconds as the next climb starts.

A connected cadence sensor fixes most of this. When your pedals stop turning, Cadence sets power to zero instead of counting the speed-up as pedaling, which also removes false readings on long coasting descents. A cadence sensor doesn’t measure how hard you’re pushing, though, so if you keep pedaling over the top, a smaller spike can remain. Showing power averaged over 3 seconds or more smooths out what’s left, and brief maximum values are still the least reliable number in an estimate.

So what is it good for? Consistency.
The estimate runs the exact same physics on every ride, so your numbers are comparable with each other. If your average watts on your regular loop creep up month over month, that’s real improvement, measured the same way every time. Think of it as a training gauge, not a lab instrument. Whole-ride averages land close to power-meter data on our test rides; any single ride can drift further, say, if the wind on your road didn’t match the forecast, or you spent the day in someone’s draft. If you need exact watts, that’s what power meters are for.

Every power field works

Current, average, and max power, power zones, charts, watts/kg, and even the advanced Elite metrics (Weighted Power, W’ Balance) all run on the estimate. Just remember they inherit its nature: great for trends and pacing, not for bragging-rights max sprint numbers.

Why did a ride’s power change after I edited it?

Editing anything the physics uses recalculates the ride’s watts (and its calories): your weight or height, which bike you rode, the ride’s Bike Setup (bike weight, riding position, road surface, e-bike compensation), and elevation correction. Each ride keeps the bike settings it was recorded with, so changing your bike in Settings ▸ Gear won’t change past rides. To change one ride, open Edit Activity ▸ Bike Setup, or tap Reset there to use your bike’s current settings.

Exports

Exporting a ride file includes its estimated watts like any other power data, and the file is marked internally as estimated. Uploads to Strava, intervals.icu and MyBikeTraffic leave estimated power out unless you turn on Include Estimated Power for that service, so the service can make its own estimate instead. Your calorie and power numbers always agree with each other, because they come from the same physics.

Exporting or uploading estimated power requires an Elite subscription. Without one, the ride still exports normally, just without the estimated power data.