Running app vs. GPS watch: do you need both?

Updated August 26, 2026 · By the Runked team

Phone app vs GPS watch, by factor

This table is Runked's own, built by lining up the two cited validation studies and three independent review sites' testing, by factor; none of the five sources published a table shaped exactly like this on its own.

What the accuracy studies found

Rebecca Johansson and colleagues tested distance accuracy across eight categories of GPS devices, including dedicated running watches, multisport watches and cell phones, carried by 255 runners at the 2017 Two Oceans Marathon, a 56-kilometer ultramarathon in South Africa, publishing the results in the International Journal of Sports Science & Coaching in 2020. Measured against timing-mat distances on the course, the eight device categories recorded a median error of 0.6% ± 0.3% to 1.9% ± 1.5% (interquartile range) overall. That overall figure hides a split the study reports directly: from the 16-kilometer mark to the finish, the cell-phone category, the Garmin Fenix (a multisport watch) and an activity-watch category all recorded higher distance error than the other device categories. In this sample, the devices that struggled were a phone and two specific watch categories, a narrower split than a blanket phone-versus-watch comparison would suggest. The authors note that the small error found for each brand still needs to be considered when the data feed into training-load decisions.

A phone does not carry a heart rate sensor for a run; a phone app can only display heart rate if it is paired over Bluetooth to a chest strap or a watch. Steven Pasadyn and colleagues tested how well the alternative, wrist-worn optical sensors, track real heart rate, publishing in Cardiovascular Diagnosis and Therapy in 2019. Fifty healthy, athletic adults (68% men, mean age 29, each able to run a mile in under seven minutes) ran on a treadmill at six speeds from 4 to 9 mph while wearing an Apple Watch III, a Fitbit Ionic, a Garmin Vivosmart HR and a TomTom Spark 3, checked against a three-lead ECG and a Polar H7 chest strap. Against the ECG, the chest strap itself reached a concordance correlation coefficient of .98; the Apple Watch III reached .96, and the other three wrist devices reached .89 each. Correlation for every wrist device fell as speed increased, and at 8 to 9 mph, none of the four reached .70. The Garmin underestimated heart rate by around 2 bpm on average and the TomTom overestimated by around 6 bpm. The authors ran the test on a treadmill with runners gripping a handrail during readings, conditions that do not fully match an unsupported outdoor run.

What the review sites found about the rest

Battery, cost, phone-free running, data ecosystem and training features are not the kind of factor a peer-reviewed study usually measures, so this section leans on manufacturer specification pages and three independent review sites that tested the question directly: The Wired Runner, Geek Fitness and RunV. On battery, Garmin's owner's manual for the Forerunner 70 lists up to 13 days in smartwatch mode and up to 23 hours in GPS-only mode, and Apple's specification page for the Watch SE 3 lists up to 18 hours of normal use, including a workout, or up to 32 hours in Low Power Mode, both as of August 2026. A phone has no equivalent GPS-only rating from its manufacturer; RunV's review describes a phone lasting only hours with GPS running continuously, against days for a watch. On cost, Garmin's press release for the Forerunner 70 lists a suggested retail price of $249.99, and Apple's store page lists the Watch SE 3 starting at $249, both as of August 2026. A phone adds no hardware cost beyond the phone already owned, and The Wired Runner's review names a GPS watch's roughly $200 starting price as the clearest downside next to a phone-based app.

On phone-free running, a phone app has to be carried on the run itself, in a pocket, an armband or a belt, and Geek Fitness's review notes that pulling a phone out to check pace mid-run is more awkward than a glance at a wrist. A GPS watch runs the whole session on its own, and RunV describes a watch storing a run locally and syncing it to a phone or the cloud afterward, over Wi-Fi, without needing a connection while running. On the data ecosystem, a phone app sends a run wherever that specific app is built to send it: The Wired Runner lists Strava, MapMyRun and RunKeeper as common destinations. A GPS watch instead ships a run into its maker's own platform first, Garmin Connect or Apple Health, and The Wired Runner notes that most watch platforms also forward data on to third-party apps from there. On training features, The Wired Runner covers phone apps as handling the basics of time, distance and pace, with GPS watches adding cadence, running power, vertical oscillation, ground contact time, recovery guidance and, on some models, a built-in virtual coach.

How to apply this to your own running

A runner just starting out does not need to buy anything: a phone already covers the first few months of training, and RunV's review recommends exactly that, upgrading to a watch only once training becomes consistent enough for phone-free running and a longer battery to start mattering.

A runner training for a first 10K or half marathon who wants to leave the phone at home on long runs has the clearest case for a watch: phone-free running and the multi-day battery in the table above are built for that, and neither shows up in a phone-only setup.

A runner building interval or tempo sessions around a heart rate zone should treat a wrist-based reading with some caution at high effort: Pasadyn and colleagues' study above found correlation with ECG weakening as pace rose, with no wrist device reaching .70 at 8 to 9 mph. A chest strap, paired to either a phone or a watch over Bluetooth, is the more accurate option at that intensity, regardless of which device handles the GPS tracking.

Whichever device logs the run, compare this week to your own last week, not to somebody else's watch or splits; a Runked rank starts everyone at Bronze and only moves on your own runs. See how the running rank works.

Common mistakes

• Buying a $200-plus watch before running a single week. Johansson and colleagues' data above ties the higher error to three specific device categories out of eight tested; a phone is enough to find out whether a training habit sticks first.
• Trusting a wrist reading during a hard interval. Pasadyn and colleagues found wrist-device correlation with ECG weakened as pace increased, falling below .70 for every device tested at 8 to 9 mph.
• Assuming any GPS watch beats any phone on accuracy. In the ultramarathon study above, the Garmin Fenix (a multisport watch) and an activity-watch category both recorded error in the same higher range as the cell-phone category over the same stretch of the course.

What to do next

Runked vs Garmin Coach covers a related decision, for anyone who already owns a Garmin and is weighing its built-in coaching plan against a phone-first app. The best free running apps rounds up the phone-app side of this comparison, for anyone planning to stay phone-only for now.

Frequently asked questions