Many smartphones now come with a built-in step counter. And smartwatches often track steps plus your heart rate. So why bother investing in a stand-alone fitness tracker?

Consumer Reports tested step counting on an iPhone 7 and a Samsung Galaxy 8. The phones were carried in a front pants pocket, a shoulder bag, and a runner’s armband.

When each phone’s scores were averaged, we found that both counted steps about as accurately as an excellent stand-alone fitness tracker.

More on Fitness Trackers
Knowing how to use one of these gadgets to improve your health is not as simple as 1-2-3.

Still, Charles Davidman, who oversees CR’s fitness-tracker testing, cautions that smartphones may miss some steps simply because many people don’t carry the devices everywhere. And most don’t offer heart-rate monitoring, an important feature for fitness buffs.

Consumer Reports also tested the Leaf Silver Edition Health Tracker, a device geared to women that tracks steps but not heart rate. As a clip-on and necklace, it rated Excellent in our step-counting tests; as a bracelet, it scored Very Good.

Smartwatches are another option. They can record steps and heart rate, and several models—including the Samsung Gear S3 FrontierApple Watch Series 2Garmin Fenix 5 and Motorola Moto 360—did well in our tests. They also allow the use of a whole array of apps.