Step goals
Why your iPhone, Apple Watch and apps never agree on your steps
Short answer: your iPhone and Apple Watch each count with their own sensor, so each misses different steps. Health does not add them together. Where both recorded the same minutes, it keeps one source, chosen by a priority list you can change. Apps that ask Health for its total should match it. Apps that count another way will not.
This question fills forum threads, and most of the answers there are guesses. The real explanation has two parts. One is how accurate each device is. The other is how Health decides which device to believe.
This page covers both: the measured error for phones and watches, and the exact query one game uses to read your steps. That game is Chonky Corgo, which we make.
Why do my iPhone and Apple Watch show different step counts?
Because each one counts only the movement it can feel. An iPhone counts steps while it is in your pocket or your hand, and nothing while it sits on a desk. An Apple Watch counts from your wrist, so it keeps going when the phone is put down. Two sensors in two places give two numbers.
How accurate is each device at counting steps?
In daily life, a watch comes closer than a phone. In a 2024 study, 104 adults wore a research-grade sensor on the thigh for a full day. Apple Watch 6 was off by 6.4% on average against it. The phone apps were off by 29.6%. On a treadmill, the picture looks different.
| Study | What was tested | Error found |
|---|---|---|
| Case et al., JAMA 2015 | 14 young adults walking 500 and 1,500 steps on a treadmill at 3.0 mph, phones in a trouser pocket | Phone apps: 6.7% under to 6.2% over. Wristbands and clip-on trackers: 22.7% to 1.5% under |
| Hong et al., Sensors 2024 | 104 adults, 24 hours of normal life, checked against a sensor on the thigh | Apple Watch 6: 6.4% average error. Galaxy Watch 4: 10.5%. Phone apps on iPhone and Android: 29.6% |
| Choe and Kang, Physiological Measurement 2025 | Review of 56 studies of Apple Watch | Apple Watch read 1.83 steps a minute low on average, with a wide spread across conditions |
The two findings fit together. On the treadmill, the phone stayed in a pocket and did well. A phone in a normal day is not always on you, and it can only count the steps it is carried for.
Two caveats. Hong's phone group mixed iPhone and Android users, so it does not single out the iPhone. And Case's wearables were older trackers, such as the Fitbit Flex and the Nike Fuelband. Read that row as history.
Does the Health app double count steps from iPhone and Apple Watch?
No. Apple's support page says that when several sources record the same type of data, the source at the top of your list takes priority. In Apple's 2020 developer session on HealthKit, the presenter walks through a day where the Health query skips iPhone steps that the watch had already counted.
If we were to sum up all of my steps over all of my devices then we would easily be doublecounting a lot of those steps. HKStatisticsQuery can help with the de-duplication of data.
Getting started with HealthKit, Apple WWDC 2020
In that example, the query ignores 900 iPhone steps that duplicated the watch. It keeps 1,100 iPhone steps from a stretch when the watch was left at home. So the Health total is neither your phone's count nor your watch's count. It is one count, stitched together from both.
You can see the order and change it. These are Apple's steps, applied to step counts:
- Open the Health app and tap Browse.
- Tap Activity, then tap Steps.
- Scroll down and tap Data Sources & Access.
- Tap Edit, then touch and hold a source's Change Order handle and drag it up or down.
One line on the same Apple page may explain a sudden jump. New apps or devices you add go to the top of the list automatically, above your iPhone. Connect a new band or app that writes steps, and Health may start trusting it first.
Why does another app show a different number from Health?
Most likely because it reads your steps a different way. An Apple developer-support engineer wrote on Apple's developer forums in 2024 that an app using HealthKit's statistics query should get a de-duplicated total, the same one the Health app shows. An app that adds up raw step records itself, or counts on its own, can drift.
- The app adds up every step record from every device. Apple's presenter called that double counting in the 2020 session.
- The app counts steps itself instead of reading Health, so it only knows what its own device felt.
- The app read your steps a while ago. Its number is a snapshot, and Health has moved on since.
What does Chonky Corgo read from Apple Health?
One total per day, the same kind the Health app shows. In version 2.0, Chonky Corgo asks HealthKit for a cumulative sum of steps from local midnight until now. The request filters by date only, not by device or app, so Health does its own de-duplication before Chonky ever sees the number.
The code lives in HealthKitStepService.swift. Daily history uses the same kind of sum, one per day. When Health holds no step records at all for a window, HealthKit answers with a no-data error, and Chonky reads that as 0 steps rather than a failed sync. The Apple Watch app runs the same query on the watch.
One honest gap: Apple's written HealthKit reference pages do not spell out the de-duplication. The evidence is the WWDC session and the forum reply above, both from Apple staff.
Why do strollers, shopping carts and treadmills throw the count off?
Because a wrist device mostly feels your arm, and pushing a stroller or a cart holds the arm still. Apple's own accuracy page tells walkers to let the watch arm swing naturally. For pushing a stroller, it says you can still earn Exercise credit by starting a walk in the Workout app.
How much gets lost is less settled. A 2022 paper in the CDC journal Preventing Chronic Disease summed up earlier studies as showing wrist monitors undercounting by 35% to 95% when the wrist does not move. A 2017 lab study of 15 young adults found no significant error for a shopping cart.
Holding a treadmill's handrails is the same situation: feet moving, wrist still. It is the one case where the phone in your pocket may count better than the watch on your arm.
Which step count should you trust?
Trust one source over time, not the exact number on any single day. A watch worn all day comes closer than a phone in daily life. Still, every device is off by a few percent or more. A 300-step gap between two screens says almost nothing about your health.
Wear your watch from morning to night? Then putting Apple Watch at the top of the Steps list is reasonable. If you take it off often, leave the iPhone in the list, because Health fills the gaps from whichever device was with you.
For a step goal, the trend matters more than the device. That is why the step-goals guide builds a goal from your own 30-day average, whichever screen it comes from.
What else do people ask?
These questions come up whenever two screens show two totals for the same day. Each answer names the source behind it. Where Apple has not documented something, the answer says so instead of guessing at what the Health app does inside.
- Does Apple Health add iPhone and Apple Watch steps together?
- No. Apple's support page says the top source in your list takes priority when several record the same data. Apple's 2020 HealthKit session describes the query skipping iPhone steps the watch already counted.
- Why does my Apple Watch show more steps than my iPhone?
- Often because the watch was on your wrist while the phone sat on a desk or in a bag. A phone only counts steps it is carried for. In a 2024 daily-life study, phone apps were off by 29.6% on average and Apple Watch 6 by 6.4%.
- Will Chonky Corgo match my Health app step count?
- It should. In version 2.0, Chonky asks HealthKit for the same kind of de-duplicated daily total the Health app shows, with no filter by device or app. If Health undercounts a day, Chonky undercounts it too.
