What to look for in a running watch: GPS & heart rate guide

Photo by Omar Ramadan on Pexels

You’re standing in a shop (or scrolling a listing at 11pm) looking at watches ranging from £90 to £900, all claiming to track GPS and heart rate, all with spec sheets that read like a NASA brochure. Somewhere between “multi-band GPS” and “training readiness score” you’ve stopped being able to tell what actually helps you run better and what’s just there to justify the price tag.

Here’s the useful starting point: a running watch does two core jobs. It tells you how far and how fast you went, and it tells you how hard your body is working while you did it. Everything else — the sleep scores, the recovery advisor, the golf mode nobody asked for — is secondary. If you get GPS accuracy and heart rate tracking right, you’ve covered 90% of what actually changes your training.

This guide breaks down what matters in each category, what’s genuinely useful for an everyday runner training around a job and a life, and what you can safely ignore.

GPS: what “accurate” actually means for you

GPS accuracy isn’t about hitting exactly 10.00km on a 10k race course — tree cover, tall buildings, and tunnels will always cause some drift. What matters is consistency: does the watch give you roughly the same distance and pace reading for the same route, run after run?

Three things affect this:

• Chipset quality. Multi-band (dual-frequency) GPS, now standard on most watches above £200, is measurably more accurate under tree cover and in cities than older single-band GPS. If you run a lot of urban routes or wooded trails, this is worth the extra money.
• Satellite systems used. Look for watches that combine GPS with GLONASS, Galileo, or QZSS. More satellite networks generally means faster lock and tighter tracking, especially at the start of a run before signal stabilises.
• Auto-pause and auto-lap behaviour. Cheap watches sometimes struggle with these at traffic lights or water stops, adding phantom distance. Test this on your first few runs before trusting race-day splits.

A simple rule: if you’re training for 5k and 10k, GPS accuracy to within 1–2% is fine and nearly every modern watch gets there. If you’re pacing a marathon off your watch alone, that 1–2% compounds over 42km, which is why experienced marathoners also use mile markers as a sanity check, not just their wrist.

Heart rate: wrist-based vs chest strap

This is where most runners get misled by marketing. Optical (wrist-based) heart rate sensors have improved a lot, but they still struggle in specific, predictable situations: very cold weather, tattoos over the sensor area, loose watch fit, and high-intensity efforts where your arm is pumping hard (think 400m repeats or a hard parkrun finish).

A chest strap is still more accurate, particularly during intervals or sprint finishes, because it reads the actual electrical signal from your heart rather than inferring it from blood flow through skin.

If you’re mostly doing easy runs and the occasional steady long run, wrist HR is genuinely good enough — don’t let anyone tell you you need a strap to train properly. If you’re doing structured interval work or chasing a specific heart rate zone for tempo sessions, a chest strap removes a layer of guesswork. The NHS and most exercise physiology sources agree that heart rate response is one of the more reliable ways to gauge effort over time, which is exactly why getting an accurate reading matters more than people assume.

Battery life: match it to your actual mileage

This is the spec that trips people up most. A watch with “7 days battery life” usually means 7 days in smartwatch mode with GPS off. Turn GPS on for a 90-minute long run and that number drops fast — sometimes to 15–20 hours of GPS-tracked use total.

Work out what you actually need:

• 5k–10k training, a few runs a week: almost any watch’s battery is fine. You’ll charge weekly regardless.
• Half marathon training with a long run over 90 minutes: check GPS-mode battery life specifically, not the headline number. You want at least 20 hours of GPS tracking per charge so a long run doesn’t eat half your week’s battery.
• Marathon training or ultras: look for watches explicitly rated for 20+ hours of GPS tracking, ideally with a battery-saver GPS mode for runs over 4 hours. This matters more than any other feature if you’re doing a 16-week marathon training plan with weekend long runs creeping past 3 hours.

Features that matter vs features that don’t

It’s easy to get sold on features you’ll never open. Here’s a blunt breakdown:

Worth having:
– Pace alerts — a buzz when you drift outside your target pace, useful for easy runs where it’s tempting to go too fast
– Interval/workout builder — lets you programme a session (e.g. 6 x 800m with 400m recovery) so you’re not checking your watch every 10 seconds
– Running power or cadence data — useful once you’re past the beginner stage and want to work on form, not essential before then

Rarely worth paying extra for:
– Built-in music storage — most people run with their phone anyway, or use a dedicated setup like the ones covered in guides on the best headphones for running that stay in
– Advanced “training readiness” or “body battery” scores — interesting, but not a substitute for how you actually feel. Nobody needs a score to tell them they’re tired after a bad night’s sleep and two early starts
– Golf, diving, or ski modes — ignore unless you genuinely do those sports

Matching the watch to where you actually are in your training

A beginner running their first Couch to 5K doesn’t need the same watch as someone chasing a sub-4 marathon. Buying more watch than you need isn’t a crime, but it is often money that could go toward better shoes or race entry.

If you’re not sure which bracket you’re in yet, it’s fine to start cheap. A lot of runners buy a premium watch before they’ve run three times a week for six months straight, and it ends up gathering dust next to the running shoes they also over-bought. Consistency matters more than hardware — something worth remembering if you’re still working on the mindset shift from jogger to runner.

Setting it up so it actually helps you train

Buying the right watch is only half the job. A few setup steps most people skip:

1. Set your max heart rate properly. The default age-based formula (220 minus age) is a rough estimate and can be off by 10–20 beats for some people. If you’ve had a recent max-effort session or field test, enter your actual observed max instead.
2. Define your heart rate zones based on that number, not generic defaults, so “Zone 2 easy running” actually reflects your easy effort, not someone else’s.
3. Turn on pace or HR alerts for easy runs specifically. This is the single most useful setting for runners who struggle to slow down — a genuine problem discussed in easy run vs recovery run: what’s the difference, since going too fast on easy days is one of the most common ways runners stall their progress or get injured.
4. Re-test your HR zones every few months, especially after a block of consistent training — your resting and max heart rate do shift as fitness improves.

The Honest Takeaway

• If you’re training for 5k–10k distances a few times a week, don’t overspend — accurate GPS and decent wrist HR on a £100–£180 watch will do everything you need.
• Chest straps are worth it specifically for interval sessions and sprint finishes, not for easy running — don’t buy one just because it feels “more serious.”
• Check GPS-mode battery life, not the marketing headline number, especially once your long runs pass 90 minutes.
• Set your heart rate zones based on your actual observed max, not the device default — this single step makes every other heart rate feature more useful.
• Ignore scores and modes you won’t act on. A watch that tells you you’re tired doesn’t replace listening to your body — it just adds a notification to the pile.

Next read: Best budget GPS running watch under £150 in 2026