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Heart Rate Zone Calculator (2025)
Calculate your 5 heart rate training zones for optimal fat burning, endurance, and performance. Uses both Max HR% and Karvonen (HRR) methods.
Est. Max HR: 185 bpm
Very light. Warm-up, cool-down, active recovery. (50–60% max HR)
Fat burning zone. Conversational pace. Build endurance. (60–70% max HR)
Improved aerobic capacity. Moderate effort. (70–80% max HR)
Hard effort. Race pace. Increases lactate threshold. (80–90% max HR)
Maximum effort. Short intervals only. (90–100% max HR)
Analysis & insights
Your estimated max heart rate is 185 bpm (220 minus your age of 35). Your resting HR of 65 bpm is within the healthy range for adults. For most training, spend the majority of time in Zone 2 (137-149 bpm) — that's where you build the aerobic engine that powers everything else.
Max HR: 185 bpm
Calculated using Heart Rate Reserve (Karvonen). Resting HR in the healthy range.
Risk & benchmark gauge
Current band
Healthy
Resting HR: 65 bpm
Industry benchmarks
- Your max HR185 bpm
- Your resting HR65 bpm
- Healthy resting range60-80 bpm
- Endurance athletes40-60 bpm
- Zone 2 (fat burn)137-149 bpm
- Zone 4 (threshold)161-173 bpm
Key insights
Zone 2 is where the magic happens
Most aerobic adaptation (mitochondrial density, fat oxidation, capillary growth) happens at Zone 2 — a conversational pace you could maintain for 60+ minutes. Most amateurs train too hard most of the time and miss this.
The 80/20 rule
Elite endurance athletes spend ~80% of training in Zone 2 and 20% in high-intensity (Zones 4-5). This polarized pattern outperforms moderate-intensity-everywhere ("gray zone") training.
HRR is more accurate than %MaxHR
The Karvonen formula (HRR) accounts for your resting HR, which varies wildly between individuals. Use it if you can measure your true resting HR (first thing in the morning).
Recommended actions(4)
Spend 80% of cardio in Zone 2
High priorityYou should be able to hold a conversation, breathing steadily through your nose. If you're mouth-breathing, slow down.
Impact: Builds the aerobic base that all higher-intensity work depends on.
Add 1-2 high-intensity sessions per week
High priorityShort intervals (4x4 minutes at Zone 5 with 3-minute recovery) drive VO2 max improvements that Zone 2 alone won't.
Impact: Even 6-8 weeks of structured intervals can raise VO2 max by 5-10%.
Track resting HR weekly
Medium priorityPersistent elevation (>10 bpm above baseline) signals overreaching, illness, or poor sleep. Listen to it.
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This tool is for informational purposes only and does not constitute medical advice. Consult a healthcare professional for advice specific to your situation.