Heart Rate Accuracy: Why It Differs by Brand (2025 Guide)

Heart Rate Accuracy: Why It Differs by Brand (2025 Guide)

Heart rate monitoring is one of the most important features in modern smartwatches and training watches.
But not all sensors are created equal—accuracy can vary significantly depending on the brand, sensor design, and how you use the watch.

1. How wrist-based heart rate sensors work

Most watches use PPG (photoplethysmography): green (sometimes red/infrared) LEDs shine into your skin, and sensors measure blood flow changes.

  • Green light → best for high-frequency signals (running, HIIT).
  • Red/infrared → better for low-perfusion states (cold weather, sleep, deep tissue).

Factors that affect accuracy:

  • Skin tone & tattoos.
  • Watch fit (too loose = poor readings).
  • Arm motion (cycling vs rowing).
  • Temperature (cold = reduced blood flow).

2. Brand differences in heart rate accuracy

Apple

  • Uses advanced multi-LED + photodiode array.
  • Generally very accurate for steady-state activities and casual use.
  • Can struggle during high-intensity interval training (HIIT) with rapid changes.

Garmin

  • Elevate Gen 5 optical sensor (latest).
  • Solid for running, cycling, daily tracking.
  • Can lag slightly behind a chest strap during sprints or sudden spikes.
  • Many models support ANT+/Bluetooth chest straps for higher accuracy.

COROS

  • Known for strong endurance athlete focus.
  • Accuracy on par with Garmin, sometimes better in long steady workouts.
  • Slightly weaker for short, explosive intervals.

Suunto

  • Solid accuracy, but software smoothing can lag on quick changes.
  • Best for outdoor, long-duration activities.

Fitbit

  • Optimized for 24/7 lifestyle + wellness tracking.
  • Great for sleep and resting HR.
  • Less accurate for serious training compared to Garmin/Apple.

Samsung Galaxy Watch

  • Optical sensors + advanced algorithms.
  • Good for everyday HR and stress tracking.
  • Can struggle with wrist movement during workouts.

Polar

  • Strong HR legacy (invented wireless HR chest straps).
  • Optical accuracy is solid but not industry-leading.
  • Chest straps still the gold standard (Polar H10).

3. Wrist HR vs Chest Strap vs Arm Band

  • Wrist HR (optical): convenient, but accuracy drops during high motion.
  • Chest strap (ECG-based): most accurate, especially for HIIT and HR zones.
  • Arm bands (Polar Verity Sense, Scosche Rhythm+): more accurate than wrist, less hassle than chest strap.

4. How to improve heart rate accuracy

  • Wear the watch snugly, 1–2 finger widths above wrist bone.
  • Warm up before workouts (improves blood flow).
  • Clean the sensor and your skin.
  • Use a paired chest strap if precision is critical (interval training, VO₂max testing).

5. Why it matters for buyers

  • If you’re buying mainly for fitness tracking, prioritize accuracy.
  • If you’re buying mainly for health/lifestyle, wrist HR is good enough.
  • Endurance athletes or interval trainers should consider watches that pair easily with external sensors.

Final takeaway

  • Apple, Garmin, COROS = strongest wrist HR accuracy overall.
  • Fitbit, Samsung = fine for lifestyle, less reliable for hardcore training.
  • Polar = still the chest strap king.

When evaluating heart rate accuracy, ask: Do I need wrist-only convenience, or am I willing to wear a strap for lab-level precision?
Your answer determines which brand is right for you.