Running watch battery life: how much you really need

How much GPS battery do you actually need?

The figure that matters is not the headline standby time but the GPS battery: how long the watch records continuously with the GPS active. The rule is simple: it must comfortably exceed your longest run, with at least an hour of headroom. A few worked examples make it concrete. A parkrun or 10 km takes well under an hour, so almost any watch will do. A typical 4 to 4.5 hour marathon needs at least 6 hours of GPS to be safe. A 50 km trail ultra at 6 to 8 hours wants 10 hours or more. And a 100-mile mountain race can run 24 to 30 hours, so you need a watch built for it.

This is why battery is a buying decision, not an afterthought. A watch that lasts two weeks as a smartwatch might still only manage 7 hours of GPS, which is fine for a fast marathon but tight for a slow one and useless for an ultra. Always check the GPS figure against your longest planned effort, then add a margin for a forgotten charge or a slower-than-hoped day.

Battery life by watch, tested

We measured GPS battery on every watch by running it from full to empty in its standard accurate GPS mode, and the spread is enormous:

• Suunto Race: 40 hours of dual-band GPS, 26 days standby, up to 120 hours in endurance mode. The longest here.
• Coros Pace 3: 38 hours of dual-frequency GPS, 17 days standby, up to 100 hours in standard GPS. Ideal for ultras.
• Polar Pacer Pro: 35 hours of GPS, 7 days standby. Covers any race distance.
• Amazfit Bip 5: 26 hours of GPS, 10 days standby. Remarkable for a sub-£60 watch.
• Garmin Forerunner 265: 20 hours of multi-band GPS, 13 days standby. Plenty for a marathon, with a brighter AMOLED screen as the trade-off.
• Apple Watch Series 9: around 7 hours of GPS, 18 hours standby. The shortest here, and tight for a slow marathon.

The takeaway is clear: if you only race up to marathon distance, every watch except the Apple covers you with ease, and even the Apple is fine under three hours. If you run ultras or multi-day efforts, the Coros and Suunto are in a league of their own.

Why GPS drains a running watch so fast

The gap between a watch's two-week standby figure and its 7-to-40-hour GPS figure surprises a lot of buyers, but the reason is straightforward. To record your position, the watch keeps its GPS receiver powered continuously, often listening to four or five satellite systems at once, and it logs a fix roughly every second. That receiver is one of the hungriest components in the watch, and dual-frequency reception, which listens on two radio bands at once for better accuracy, draws even more power than single-band.

So there is a direct trade-off between accuracy and endurance. A watch in its most accurate dual-frequency mode burns through battery fastest; switch to a lower-power single-frequency or interval-fix mode and the same watch can last two or three times as long, at the cost of some precision. That is exactly the lever the Coros and Suunto pull to reach their headline 100-plus-hour endurance figures.

How the screen changes the equation

Screen technology is the other big driver of battery life. AMOLED displays, as on the Garmin Forerunner 265, Apple Watch Series 9 and Suunto Race, are bright and sharp but power-hungry, especially with always-on enabled. Memory-in-pixel (MIP) screens, as on the Coros Pace 3 and Polar Pacer Pro, are dimmer and lower-resolution but barely sip power and are always-on by default, which is a large part of why those two watches last so long. If battery is your priority, an MIP watch will almost always outlast an AMOLED one of similar size; if you want a vivid display, you accept more frequent charging.

How to make your watch's battery last longer

You can stretch any watch's endurance with a few settings. Turn off the always-on display so the screen lights only on a wrist raise; on the Garmin this alone added around 4 days of standby in our testing. Use a lower-power GPS mode for easy runs and save dual-frequency for races, which can double GPS battery. Disable on-board music streaming during long runs, since Bluetooth audio is a significant drain. And keep firmware up to date, as manufacturers regularly improve power efficiency. For a long race, start fully charged the night before rather than topping up in the morning.

Battery health over the years

One number the spec sheet never quotes is how the battery ages. Like any lithium-ion cell, a running watch's battery slowly loses capacity with each charge cycle, typically dropping to around 80% of its original life after two to three years of regular use. In practice that means a watch quoting 20 hours of GPS when new might manage closer to 16 after a few hundred runs, which is still ample for a marathon but worth bearing in mind if you bought right at the edge of your needs. You can slow the decline by avoiding leaving the watch on charge at 100% for days, and by not routinely running it flat to 0%. Buying a watch with a comfortable battery margin over your longest run is the simplest insurance against this gradual fade.