Your Phone as a Pedometer: Better Than You Might Think

Here is a happy surprise: you may already own a step counter without knowing it. Most smartphones count steps in the background, and plenty of people rely on those numbers. So how good are they? Let’s look at a well-known test and at how to get the most from your phone’s step count. This is general education, not medical advice, and it does not recommend any app or device.

The test

In 2015, Case and colleagues at the University of Pennsylvania published a research letter in JAMA that tested ten popular apps and devices. Volunteers walked on a treadmill at 3 miles an hour for 500 steps and for 1,500 steps, each twice, while a person counted the real steps by hand. The devices were worn on the waist, on the wrist or carried in a pocket.

How close did they come?

• Waist-worn pedometer and accelerometers: within about 1 percent of the true count.
• Smartphone apps: between about 7 percent below and 6 percent above the true count.
• Wrist-worn trackers: between about 23 percent below and 1.5 percent below, with one device counting more than 20 percent fewer steps than were taken.

The authors concluded that many smartphone apps and wearable devices were accurate for counting steps, and that the phones were only slightly different from the observed counts, though they could read slightly high or slightly low.

Reasons for good news

• It is free and already with you. A phone in a pocket or bag does the job for many walkers.
• Small errors do not change the picture. If your count is 5 percent off, a weekly average is still very useful for seeing whether you are moving more.
• Trends matter more than totals. Comparing this week with last week works with any steady counter.

Good to remember

• It was a small, controlled test. The volunteers walked on a treadmill at a steady pace, and the study counted steps only, not distance or calories.
• Devices and apps change. The products tested in 2014 have been updated many times, so the exact numbers do not carry over.
• Where you carry it matters. A phone left on a desk or in a bag can miss steps, and one carried in a pocket usually does better.
• Calories burned are another matter. See our guide to the calories-burned number on fitness trackers.

Getting more from your steps

• Pick a baseline week. Carry your phone the same way for a week to see your usual number, then nudge it up gradually.
• Do not chase a magic number. The popular 10,000 has a surprising history; see the 10,000-steps story and how much walking is enough.
• Combine it with something you enjoy. A call on foot, a walk after a meal or a different route home all add up.
• Consider a wearable if you want more. A watch or ring can add sleep and heart rate. See smart rings and wearables for how much to expect.

Final thoughts

For counting steps, the phone in your pocket is a surprisingly good tool. It is not perfect, but it is accurate enough to show whether your daily movement is heading in the direction you want, and that is something to smile about.

Sources

• Case MA, Burwick HA, Volpp KG, Patel MS. Accuracy of smartphone applications and wearable devices for tracking physical activity data. JAMA, 2015;313(6):625-626.