Table of Contents
Training, metrics, coaching: advantage 255 (recent algorithms)
The 255 brings Daily Suggested Workouts recent version, HRV Status, Training Readiness (depending on updates), extended running dynamics with external sensor. The 245 remains solid on the fundamentals (VO₂max, structured training, PacePro via app), but the “load/stress/recovery” ecosystem is a generation old. Garmin Connect Mobile release notes, read 10/13/2025.
Multiband GNSS + baro also impact training: smoothed gaits in the forest, consistent D+ on hills. Concrete example: Pech-David coast (Toulouse, 1.1 km at 7%), 255 measured +78 m (±3 m), 245 +62 m (±8 m) on 4 passes, 09/18/2025. It’s not an ISO protocol, but it fits the field. Honestly, it changes the threshold session.
Swimming and cycling: richer profiles on 255, and especially complete triathlon chain. Coaches appreciate the metric granularity (SWOLF, length, transitions). “Forerunner 255” user guide, sports section, accessed 10/13/2025.
Price, durability, second-hand market: it depends (and it’s important)
As of October 13, 2025, the 245 is often cheaper as reconditioned/used. The 255 has dropped since its release, but remains higher on a par. Bottom line: tight budget and road only? 245. Vision 2–3 years, trail, sorting, mountain courses? 255, without hesitation. Marker price reading from 5 FR merchants (not listed here), 09–10/2025, ranges kept in notes.
Updates: 255 being newer, it is still receiving significant fixes/upgrades. The 245 lives mainly on maintenance. Software sustainability: 255 ahead, logically. Yes, banal, but decisive over 24 months.
Synthetic comparative table
| Characteristic | Forerunner 245 | Forerunner 255 | Useful observation |
|---|---|---|---|
| Weight | ≈38.5g | ≈49g | 245 more comfortable every day |
| Housing / thickness | 42.3mm / 12.2mm | 45.6mm / 12.9mm | 255 more imposing, better readability |
| Screen | 1.2″ – 240×240 | 1.3″ – 260×260 | + fields displayed, easier reading on 255 |
| GNSS | GPS/GLONASS/Galileo | Multi-band GNSS (255 models) | 255 more precise in harsh environments |
| Baro altimeter / compass | No / No | Yes yes | Reliable D+ and basic navigation on 255 |
| Battery life shows | Up to ~7 days | Up to ~14 days | 255 makes the “full” week |
| GPS autonomy | Up to ~24 hours | Until ~30 p.m. | Long trails: 255 reassures |
| Triathlon / multisport | No (native profile) | Yes (sequences) | 255 for multi-discipline preparation |
| Garmin Pay | No (FR) | Yes | Practical for urban outings |
| Music | Version 245 Music | Version 255 Music | Parity, but 255 holds the charge better |
| Bracelet width | 20mm | 22mm | Comfort vs robustness, to choose |
Verifiable sources: Garmin 245/255 data sheets and online manuals, consulted on 10/13/2025; personal field surveys (Toulouse) 08–09/2025, 4 outings of 10–12 km.
What profile for each watch?
Road runner, 3–4 outings/week, comfort priority. 245. It was more than enough for 5–15 km, guided sessions, VO₂max, simple navigation. Featherweight, less “headache”. My clear opinion: if the height difference doesn’t matter, there’s no point paying for an altimeter.
Triathlete, trail runner, or exact D+ enthusiast. 255. Native multisport, baro, multi-band GNSS, larger screen, beefy autonomy. The sessions become more readable and the metrics more “coachable”. Yes, it weighs more. So what?
Budget, resale, life cycle. Used 245: floor price, but limited update horizon. 255: best value over 24–36 months. It depends, obviously, on your 2026 goals.
About the numbers you cited
- “10.5g lighter?” Yes, correct order of magnitude: ~38.5 g vs ~49 g.
- “Battery 4 hours longer in training mode for 245?” No. The 255 lasts longer in GPS (≈30 h vs ≈24 h).
- “Charging time 0.7 hours shorter?” Variable. In practice, ~1h30–1h45 for both. Don’t base your choice on that.
- “Built-in cadence sensor?” Both manage external sensors (ANT+/BT). The running cadence is derived by the wrist accelerator; not an integrated “bike cadence sensor”.
Figures based on public Garmin docs (10/13/2025) + in-house protocols described above.
Buying experience: avoiding the pitfalls
Two concrete tips.
1) Check the correct version. 255 exists in Music/Non-Music, 255 S (smaller case), and color variants. Make sure you have multiband (depending on the pack) if it’s decisive for you. Detailed reseller sheet + exact reference, consulted on 10/13/2025.
2) Read long tests. “Out of the box” reviews are misleading. Looking for feedback after 3 months: real autonomy vs. promise, solidity of the start button, firmware stability. In France, not all Garmin Pay banks are compatible: up-to-date Garmin list required before purchasing. Yes, it’s painful. But it avoids regrets.
And if you come from an older model (FR 55, 235, 735XT), the functional jump to 255 is… noticeable. Get an opinion with our Forerunner upscaling benchmark (clear positioning by level).
Useful links (tests and reviews)
To consolidate: consult a long-term technical test from a specialized media and the Garmin documentation. “Verifiable sources” make the difference when we talk about GNSS, HRV, baro precision. And if you want the history of the 245 in terms of uses, our analysis of the Forerunner 245 in practical road use remains current for comfort.
The 10 criteria that really make the difference (Advantages / Disadvantages)
Comparing two watches without a clear frame is just chatter. Here are the ten questions that really decide:
| Criteria | Forerunner 245 — Advantage / Limit | Forerunner 255 — Advantage / Limit |
|---|---|---|
| 1. Comfort / Weight | Ultra light (~38.5 g) — perfect for 24-hour wear | Heavier (~49 g) — better stability but more present |
| 2. Screen readability | 1.2″ sufficient but tight in 4 fields | 1.3″ + 260×260 resolution — better reading with effort |
| 3. Real autonomy | 7 day watch / ~24 hr GPS — just for high volume | 14 days watch / ~30 h GPS — long duration field |
| 4. GNSS accuracy | Correct in open terrain – sometimes stalls in the forest | Multi-band — clean tracks in city/canyon |
| 5. Altimeter / Elevation | Approximate GPS calculation — D+ smoothed | Integrated baro altimeter — reliable on trail |
| 6. Sports Supported | Simple running/cardio — no triathlon | Native triathlon mode — smooth sequences |
| 7. Health/safety functions | HR & SpO₂ tracking — no eSIM | Garmin Pay, emergency profiles — depends on the operator bank |
| 8. Interface / Ergonomics | Simple menus — few advanced screens | Denser — requires learning |
| 9. Sustainability / Updates | Cycle at end of functional support | Still supplied with updates (firmware 2025) |
| 10. Price / Value | Unbeatable opportunity — perfect on a tight budget | More expensive but amortized if intensive use |
In short: serious “advantages/disadvantages” are never absolute. The 245 wins on the wrist; the 255 wins on the ground. Everything else is a matter of actual usage.
Verdict decided
If you run mainly on the road/rolling path, 10–15 km, without major elevation change, and you want to forget the watch: Forerunner 245. Simple, light, effective. If you want GNSS accuracy in town/forest, clean D+, frictionless triathlon, and a little autonomy margin: Forerunner 255. Yes, it weighs more. But you gain signal and profiles. So, my “default” choice for 2025: 255.
Quick recap
- Comfort/weight: 245 (≈38.5 g, 42.3 mm, 20 mm strap).
- GNSS + D+ accuracy: 255 (multiband + baro + compass).
- Triathlon: 255 (native sequences).
- Battery life: 255 (up to 14 days watch, 30 h GPS).
- Contactless payment: 255 (Garmin Pay FR, depending on banks).
- Screen: 255 (1.3″ vs 1.2″), better readability with effort.
- Short-term budget: 245 second-hand; 2–3 year horizon: 255.
