Forerunner 70 vs 170 for training

Figure	Forerunner 70	Forerunner 170
GPS battery	23 h GPS only, manufacturer claim	20 h GPS only, manufacturer claim
Smartwatch battery	13 days, manufacturer claim	10 days, manufacturer claim
Weight	40 g, manufacturer claim	41 g, manufacturer claim
Satellite systems	GPS, GLONASS, Galileo; no multi-band, manufacturer claim	GPS, GLONASS, Galileo; no multi-band, manufacturer claim
Training metrics	Training Readiness, Training Status, HRV Status, VO2 Max, race predictor, manufacturer claim	Same list, manufacturer claim
Cycling sensors	Speed, cadence and radar, no power meter, per The5krunner	Bluetooth and ANT+, power meters included, per Tom's Guide
Barometer	None, per Tom's Guide	Yes, per Tom's Guide
Open-water swim	Pool only, per DC Rainmaker	Yes, manufacturer claim
Storage	512 MB, per T3	4 GB, per T3

Take these two to the start line of a road marathon and I doubt you'd miss anything on the 70. The screen is the same, and so is the list of training metrics Garmin publishes. What you pay extra for on the 170 mostly sits outside running.

I haven't worn either watch. Every measured result below belongs to the outlet named beside it, and all of this was checked on 3 November 2026.

£219.99 on garmin.com (UK), checked 3 November 2026. £259.99 on garmin.com (UK), checked 3 November 2026.

What the two share

Garmin lists Training Readiness, Training Status, HRV Status, VO2 Max, running power, race predictor on the 70, and the identical list on the 170. T3 says the 70 also gets Garmin Coach and daily suggested workouts. Its verdict: the core running experience stays "impressively intact".

Garmin's press release describes those plans as adapting daily to your health and recovery metrics. It also adds lower-volume run/walk plans. That matters more to a first marathon than anything else in this article.

One catch I couldn't settle. TechRadar's Forerunner 570 review says Garmin moved adaptive training plans into its paid Connect+ tier. I couldn't confirm how that applies to either of these two watches, so check what you get free before you count on it.

Neither watch has multi-band GPS. If you run among tall buildings, read my multi-band GPS explainer first. It might push you to another watch altogether.

Where the 170 pulls ahead

Tom's Guide lists a barometer, altimeter and gyroscope on the 170 that the 70 doesn't get. It also says the 70 can't pair with cycling sensors, but The5krunner says it takes speed and cadence sensors and Varia radar, just not a power meter, and DC Rainmaker also names power meters as the gap. The 170 takes chest straps and power meters over Bluetooth and ANT+.

The barometer is the one a runner may feel. Without it, your hill data has less to work from on a hilly course. I read no test measuring that gap between these two, so I'm flagging the hardware and nothing more.

Garmin says the 170 logs open-water swims. DC Rainmaker and The5krunner both list the 70 as pool swim only. T3 puts storage at 4 GB against 512 MB, and the 170 adds Garmin Pay.

None of that speeds up a long run.

Battery on a long run

Garmin claims 23 h, GPS only on the 70 and 20 h, GPS only on the 170. Run 42.2 km (26.2 mi) at 5:30 min/km and you're out for about 3 h 52 min, so either covers race day with a wide margin. For matching race length to GPS hours, use my GPS mode guide.

The difference shows up between charges. The Run Testers had to charge the 170 about every 3.5 days with the screen always on and a daily run. They say that's shorter than the 70. T3's reviewer measured roughly 25% of the battery gone in a three-and-a-half-hour walk on all systems, which works out at 14 h.

Heart rate and GPS: the evidence

This is thin, and most of it covers the 170.

The Run Testers, three runners over several weeks, found the 170 matched the tracks of a Forerunner 970 and a Coros Pace 4 in multi-band mode, and heart rate from a chest strap. Their test is independent and non-peer-reviewed. Tom's Guide's reviewer says Garmin's older sensor generation has been a little less accurate than Gen 5 in his long-term use.

The5krunner is the exception, with figures for both against a Forerunner 970 and HRM 600 strap (independent, non-peer-reviewed). On one steady parkrun, the 170 showed -0.1 bpm bias with limits of -2.6 to +2.5 bpm, and the 70 showed -0.9 bpm with limits of -12.8 to +11.0 bpm. In short intervals they came out close: +0.5 bpm with limits of -7.8 to +8.7 bpm on the 170, and +0.5 bpm with -8.6 to +9.7 bpm on the 70. It's one tester, and he says both use the same sensor, so I wouldn't call the parkrun gap a hardware difference. No peer-reviewed study I found covers either model.

Those are the only interval figures I could quote. Short intervals are where wrist sensors are weakest in general, as I explain in why wrist heart rate fails.

A sports watch isn't a medical device. Treat VO2 Max here as an estimate of a trend. In the pooled INTERLIVE statement (Molina-Garcia 2022, peer-reviewed, 14 validation studies), exercise-based estimates averaged close to the lab, but limits of agreement ran from -9.92 to 9.74 ml/kg/min. None of those studies tested these two watches.

Who should pay more

Pick the 70 if your plan is road running. It costs £219.99 against £259.99 at Garmin, and it claims more battery both ways.

Pick the 170 if you also ride with a power meter, swim in open water or train on hills and want barometric data. Those are real gaps. They just aren't marathon gaps.

Still undecided? The picker will sort it by goal, and the marathon goal page lists what else fits a first race plan.