Heart Rate Zone Calculator
Calculate your 5 heart rate training zones using the Karvonen formula with resting heart rate.
By Konstantin Iakovlev · Founder, Calks.uk
Last updated: · Verified against HMRC and GOV.UK 2026/27 rates
Measure first thing in the morning
Max Heart Rate
190 BPM
Heart Rate Reserve
125 BPM
Zone 1 — Recovery
Active recovery, warm-up
128–140
Zone 2 — Aerobic
Fat burning, endurance base
140–153
Zone 3 — Tempo
Aerobic fitness improvement
153–165
Zone 4 — Threshold
Speed endurance, lactate threshold
165–178
Zone 5 — Maximum
Maximum effort, sprinting
178–190
Disclaimer
This calculator is provided for informational purposes only and should not be considered as financial or tax advice. All calculations are performed locally in your browser — no personal data is collected or sent to our servers. Rates and thresholds are sourced from HMRC and GOV.UK and are updated for the current tax year. Always verify results with HMRC or consult a qualified professional before making financial decisions.
How It Works
Heart rate training zones are calculated as percentages of your maximum heart rate (MHR). The simplest estimate of MHR is 220 minus your age. The calculator divides the range from resting heart rate to MHR into five zones: Zone 1 (50–60%, warm-up), Zone 2 (60–70%, fat burn), Zone 3 (70–80%, aerobic), Zone 4 (80–90%, threshold) and Zone 5 (90–100%, VO2 max).
For greater accuracy, the Karvonen method uses your resting heart rate to calculate a heart rate reserve (HRR = MHR − resting HR), then applies zone percentages to HRR and adds back the resting heart rate. This produces personalised zones that reflect your fitness level.
Zone 2 training is recommended for building an aerobic base and efficient fat oxidation. The NHS recommends at least 150 minutes of moderate-intensity activity per week (roughly Zone 2–3) or 75 minutes of vigorous activity (Zone 4–5). Enter your age and resting heart rate to see your personalised zones.
Maximum heart rate formula. Standard formula: 220 − age = max HR. Sample 30-year-old: 220 − 30 = 190 bpm max. Tanaka formula (more accurate): 208 − (0.7 × age) = 187 bpm at age 30. Inaccurate for: very fit individuals (often 5-10 bpm higher); some genetic variants (10-20 bpm above/below average). Best measured: graded exercise test (treadmill, breath gas analysis) — £100-£300 private clinics. Field test: max sprint warmed-up, peak HR via chest strap.
Heart rate zones for training. Zone 1 (recovery): 50-60% max HR — very easy, conversational. Zone 2 (aerobic base): 60-70% — sustainable for hours, talking in sentences. Zone 3 (tempo): 70-80% — talking in 2-3 word phrases. Zone 4 (threshold): 80-90% — single words only, ~1 hour max. Zone 5 (max): 90-100% — anaerobic, minutes only. Marathon pace = top Zone 2/bottom Zone 3. 10K pace = mid Zone 4. 5K pace = top Zone 4/bottom Zone 5.
80/20 training principle. Elite athletes: 80% training easy pace (Zone 1-2), 20% hard (Zone 4-5). Most amateurs do too much 'medium-effort' Zone 3 — neither building aerobic base nor pushing limits. Increase easy volume; add 1-2 quality sessions/week. Long runs at Zone 2: builds mitochondria, capillaries, fat-burning capacity. Sprint intervals at Zone 5: builds VO2max, lactate threshold. Recovery: Zone 1 only on rest days (or full rest).
Resting heart rate — fitness indicator. Adult average: 60-100 bpm. Athletes: 40-60 bpm. Elite endurance: 30-40 bpm. Measure first thing morning before standing (apple watch tracks automatically). Drops with training over months. Sudden rise of 5+ bpm at rest: overtraining, illness, dehydration, stress. UK NHS check guidelines: HR over 100 bpm consistently — see GP. Under 60 bpm + symptoms (dizziness, fatigue): possible bradycardia, check.
Heart rate monitors and apps. Chest strap (Polar H10, Garmin HRM-Pro): most accurate, £40-£100. Wrist optical sensor (Apple Watch, Garmin, Fitbit): convenient, less accurate for intervals. Apps: Strava, Garmin Connect, Polar Flow — sync from device. Heart Rate Variability (HRV): time between beats — recovery indicator. WHOOP, Oura ring track HRV. UK NHS app: free heart rate check via finger on camera (rough estimate only).
Example: Age 35, resting heart rate 65 bpm
- Estimated MHR: 220 − 35 = 185 bpm
- Heart rate reserve: 185 − 65 = 120 bpm
- Zone 2 (60–70%): 65 + (120 × 0.60) to 65 + (120 × 0.70) = 137–149 bpm
- Zone 4 (80–90%): 65 + (120 × 0.80) to 65 + (120 × 0.90) = 161–173 bpm
Frequently Asked Questions
- What does the Heart Rate Zone Calculator do?
- Calculate your 5 heart rate training zones using the Karvonen formula with resting heart rate.
- How are heart rate zones calculated?
- Most common: % of Maximum Heart Rate (MHR). Tanaka's formula MHR = 208 − (0.7 × age) is more accurate than the old 220−age. Zones: Z1 50-60% MHR (warmup/recovery), Z2 60-70% (fat burning, aerobic base), Z3 70-80% (aerobic threshold), Z4 80-90% (anaerobic threshold, lactate), Z5 90-100% (VO2 max, maximal). For more precision: Heart Rate Reserve (HRR) method uses (MHR − Resting HR) × target % + Resting HR.
- What's the 'fat burning zone' and is it the best for weight loss?
- Z2 (60-70% MHR) burns the highest % of calories from fat. But total calorie burn is lower than Z3-Z4. For weight loss, total calories burned matter most, not the percentage from fat. A 30-min Z2 walk burns ~150 cal (70% fat); a 30-min Z4 HIIT burns ~350 cal (40% fat) — the HIIT burns more fat in absolute terms. Mixing Z2 (most workouts, builds endurance) with 1-2 Z4 sessions/week is optimal.
- Should I wear a heart rate monitor?
- Useful for serious training (marathon prep, cycling, triathlon). Chest straps (Polar H10, Garmin HRM-Pro) are most accurate — typically within 1-2 bpm of medical-grade ECG. Optical wrist sensors (Apple Watch, Garmin, Fitbit) are good for steady-state but lag/miss during HIIT or weight training. For general fitness, RPE (rate of perceived exertion: 1-10) is sufficient and trains 'feel' for pace.