MinimalistPedometer vs GPS: which is more accurate?
For distance on an outdoor walk or run, GPS is usually more accurate than a pedometer, because it measures where you went rather than guessing how long your steps are. For counting steps, and for anything indoors, a pedometer wins. The best choice depends on what you’re measuring and where.
Here’s how each one works, the situations where each struggles, and a 20-minute test you can do to see how your own devices compare.
How a pedometer works
A modern pedometer, whether it’s a clip-on gadget or the motion sensor inside your phone, uses an accelerometer. Every time your foot lands, your body moves in a small up-and-down rhythm. Software looks for that repeating pattern and counts each cycle as a step.
To turn steps into distance, the pedometer multiplies your step count by an estimated stride length. That estimate might come from your height, a number you entered, or past outdoor walks. Either way, it is an estimate, and it’s the weak link.
So a pedometer’s distance has two layers of possible error: the step count itself, and the stride length it’s multiplied by.
How GPS works
A GPS tracker asks satellites for your position about once a second and adds up the gaps between those positions. It doesn’t care how many steps you take or how long your legs are. It only cares where you are. (We explain this in more detail in how your phone measures distance with GPS.)
GPS has its own error sources: signals bouncing off buildings, weak reception under heavy tree cover, and small position wobbles. But on open ground those errors are small, and they don’t grow just because you walked faster or slower than usual.
Where each one goes wrong
Neither method is “accurate” or “inaccurate” in general. Each is reliable in some situations and poor in others.
| Situation | Pedometer | GPS |
|---|---|---|
| Open park, riverside path, suburbs | Fair (depends on stride estimate) | Good |
| Dense city center with tall buildings | Fair | Fair to poor (zigzags) |
| Treadmill or indoor track | Good for steps | Doesn’t work |
| Around the house, at work | Good for steps | Not designed for it |
| Very slow walking or shuffling | Often undercounts | Fair |
| Pushing a stroller, phone in the stroller | Often undercounts | Good |
| Changing pace (brisk, then strolling) | Fair (stride changes) | Good |
| Running | Fair (stride varies a lot) | Good |
| Steep hills | Fair (shorter uphill strides) | Good |
| Cycling or riding in a car | May log false steps | Records movement (not walking) |
A pattern emerges: pedometers are dependable at counting steps at a normal walking rhythm, but their distance drifts whenever your stride changes. GPS is dependable at distance outdoors, but useless indoors.
The stride-length problem, in numbers
Stride error is easy to underestimate. Suppose your pedometer assumes a stride of 75 cm, but on a brisk walk your real stride is 80 cm. That’s a 6–7% difference. Over a 5 km walk, the pedometer would report roughly 4.7 km. Stroll slowly with a 65 cm stride and the same pedometer would overestimate instead.
The step count could be perfect in both cases. The distance is still off, because the stride assumption doesn’t match how you walked that day. This is also why a step total isn’t a reliable stand-in for distance; see steps or distance: which should you track?
Test it yourself in 20 minutes
You don’t have to take anyone’s word for it. A standard 400-meter running track gives you a known distance to measure against.
- Find a track. Many schools and parks have one open to the public at certain hours.
- Use the inside lane. Lane 1 is the one measured at 400 meters per lap. Outer lanes are longer.
- Start your GPS tracker on the track, after giving it a few seconds outdoors to get a good fix.
- Note your step count on your phone or pedometer at the start.
- Walk four laps at your normal pace. That’s 1,600 meters, just short of a mile (1,609 m).
- Stop and compare both distances to 1,600 meters.
- Repeat at a different pace if you’re curious. Many people find the pedometer’s distance shifts more than the GPS’s.
Bonus: divide 1,600 meters by your step count to get your real stride length at that pace. If your pedometer lets you enter stride length, using this number will make its distance noticeably better.
One caveat: a running track is a near-ideal GPS environment. If most of your walking is downtown, test on a route you know the length of, such as one with distance markers.
Which should you use?
- For deliberate outdoor walks and runs: GPS. Distance, pace and speed will be more trustworthy, and you get a map of your route.
- For all-day movement and indoor activity: a pedometer or your phone’s built-in step counting.
- For both: let them do different jobs. Your iPhone can count steps in the background while a GPS app records the walks you set out to do.
Minimalist is a GPS tracker: it records your route, distance, moving time and average pace on outdoor walks and runs. It doesn’t count steps, so it pairs naturally with the step count your iPhone already keeps.
FAQ
Is my iPhone a pedometer?
Yes, in effect. iPhones have built-in motion sensors and count steps automatically when you carry the phone, showing the totals in the Health app. That’s separate from GPS, which is used when an app records your location.
Why does my GPS distance differ from a friend’s on the same walk?
Different phones, different apps and different filtering. Small differences of a few percent are normal. If yours is way off, see why your GPS distance seems off.
Can I use GPS on a treadmill?
No. Your position on the map doesn’t change, so GPS records almost no distance. Use the treadmill’s display or a step count instead.