What the research shows
Case and colleagues (JAMA, 2015) had adults walk on a treadmill for 500 and 1,500 steps while carrying phones running step apps and wearing several fitness trackers. A researcher counted every step by hand. Phone apps stayed within roughly 7% of the true count either way. Some wearables were close too, while others undercounted by up to about a fifth.
That is a lab test at a normal pace. Real life is messier, but the main lesson holds: for steady walking, counting steps is something phones do reasonably well.
Why counters miss steps
- Very slow walking: footfalls are soft, so the signal is weak.
- Short bursts: many counters wait for a few steps in rhythm before counting, so two steps across a room may not register.
- Arms still: a wrist device misses steps when you push a trolley or pram or hold a rail.
- Phone in a loose bag: the phone moves around instead of following your body.
- Screen off or app closed: some apps, including browser counters, stop counting.
Why counters add steps
Our own browser step counter is open about this. It removes gravity from the raw signal, smooths it, and only starts counting after four peaks arrive at a walking rhythm, so taps and single bumps count as zero. It cannot separate a steady vehicle vibration from walking, because to an accelerometer they look almost the same. Pause it when you get into a vehicle.
- Vehicle vibration: a smooth, steady bump rhythm on a bus, train or car can look like walking.
- Arm movement: a wrist device can count gestures, clapping or cooking as steps.
- Bouncy activities: jumping, dancing or riding over cobbles can register.
Steps are more accurate than distance and calories
Distance from steps is step count times an assumed step length. If the step length is wrong, the distance is wrong by the same share. Our counter uses 0.75 m by default and 0.415 x your height if you enter it. Calories use about 0.0006 kcal per step per kg of body weight (70 kg if you have not entered yours), which ignores pace, hills and fitness.
That is why it shows distance to one decimal place and calories as whole numbers labelled as estimates. A step count can be close; a calorie figure from steps is a ballpark.
How to get a more reliable count
- Carry the phone in a trouser pocket or hand, not loose in a bag.
- Walk at a normal pace when you want to compare days.
- Check your counter: walk 100 steps counting by hand and compare.
- Pause counting in cars, buses and trains if your counter does not detect them.
- Enter your height and weight so distance and calorie estimates fit you better.
- Compare trends over weeks rather than chasing an exact daily number.