Target Heart Rate Calculator
Training heart-rate zones from age and resting heart rate using the Karvonen formula
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What this calculator computes
The target-heart-rate calculator computes training heart-rate zones using the Karvonen formula, which incorporates resting heart rate to produce zones that scale with individual cardiovascular fitness. The Karvonen method is more accurate than the simpler Tanaka or 220-minus-age methods because it accounts for heart-rate reserve (HRR), the difference between maximum heart rate and resting heart rate. The formula is target_HR = HRR × intensity% + resting_HR, where HRR = max_HR − resting_HR, and max_HR is estimated from age (the Tanaka 2001 formula 208 − 0.7 × age is more accurate than the older 220 − age, particularly for adults over 40). The calculator returns five training zones based on percentage of HRR: zone 1 (50–60%, very light recovery), zone 2 (60–70%, light aerobic / fat-burning), zone 3 (70–80%, moderate aerobic / endurance), zone 4 (80–90%, hard threshold / lactate), and zone 5 (90–100%, maximum / anaerobic). Most endurance-training plans prescribe 70–80% of weekly volume in zone 2, with shorter doses in zones 4 and 5 for VO₂max improvement. **For informational purposes only. Consult a physician before starting a new exercise programme, particularly if you have any cardiovascular condition, are pregnant, are over 40 with risk factors, or have not exercised regularly in the past five years. Stop and seek medical attention if you experience chest pain, severe shortness of breath, dizziness, or arm pain during exercise.** Resting heart rate should be measured first thing in the morning before getting out of bed, ideally averaged over 3–5 days for stability.
Calculator
The formula
Formula
HRR = max_HR − resting_HR target_HR = HRR × intensity% + resting_HR
Worked example
When to use this calculator
Use this calculator when planning structured cardio training and you want heart-rate zones that account for individual fitness rather than just age. The most common scenarios are running, cycling, rowing, and swimming training plans that prescribe specific zones for specific sessions (long zone 2 endurance, threshold intervals, VO₂max repeats), heart-rate-monitor-based fitness tracking on Garmin, Polar, Wahoo, or smartwatch ecosystems, and rehabilitation programmes where exertion needs to stay within prescribed limits during recovery from cardiac events or surgery. The Karvonen method is more accurate than the simpler 220-minus-age estimate, particularly for very fit individuals (whose low resting HR pulls the zones lower than the simple method suggests) and for adults over 40 (where 220 − age systematically underestimates max HR). The calculator does not measure max HR directly; for the most accurate zones, perform a graded-exercise test under medical supervision to determine actual max HR, then use that figure in place of the Tanaka estimate.
Common input mistakes
- Using a single-day resting heart rate measurement. Resting HR varies day to day with sleep quality, stress, hydration, training load, and caffeine intake; a single reading can be 5–10 bpm off the true average. Measure resting HR first thing in the morning, before getting out of bed, for 3–5 consecutive days and average the results. Use the average in the calculator for zones that match your actual cardiovascular state rather than a one-off morning reading.
- Trusting the age-based max HR estimate as exact. The Tanaka formula (208 − 0.7 × age) and the older 220 − age formula are population averages with individual variation of about ±10 bpm at one standard deviation. A 35-year-old's true max HR can fall anywhere between 173 and 193 bpm; using the 183 calculated figure as exact means the zones may be 5% high or low for any given individual. For accurate zones, perform a graded-exercise test or use an extended max-effort hill-repeat session to determine actual peak heart rate.
Frequently asked questions
What is the Karvonen formula?
The Karvonen formula computes target heart rate using heart-rate reserve (HRR), the difference between max heart rate and resting heart rate. The formula is target_HR = HRR × intensity% + resting_HR, where intensity is expressed as a decimal (0.7 for 70%). It produces zones that scale with individual cardiovascular fitness because well-trained athletes have lower resting heart rates and therefore higher HRR for the same max HR, giving them a wider effective training range than less-fit individuals.
How do I find my max heart rate?
The calculator estimates max HR using the Tanaka formula (208 − 0.7 × age), which is more accurate than the classical 220 − age, particularly for adults over 40. For a more accurate individual figure, perform a graded-exercise test under medical supervision (treadmill, stationary bike, or rowing ergometer) where workload increases until maximum effort. A field test alternative is a 3-minute all-out effort at the end of a 20-minute warmup, with the peak heart rate during the final 30 seconds taken as max HR.
How do I find my resting heart rate?
Measure resting heart rate first thing in the morning, before getting out of bed, by counting pulse at the wrist or carotid artery for 60 seconds (or 30 seconds × 2 for less timing error). Take readings on 3–5 consecutive mornings and average them; resting HR varies with sleep quality, hydration, and stress, so a single reading can be misleading. Wearable heart-rate monitors and smartwatches typically record nightly resting HR automatically.
What are the heart-rate training zones?
Zone 1 (50–60% HRR): very light recovery and warm-up. Zone 2 (60–70%): light aerobic, fat-burning base, conversational pace. Zone 3 (70–80%): moderate aerobic, comfortable hard, sustained for 30–60 min. Zone 4 (80–90%): threshold/lactate, heavy breathing, sustained for 10–30 min. Zone 5 (90–100%): VO₂max and anaerobic, sustainable for under 5 min. Most endurance training prescribes 70–80% of weekly volume in zone 2 with shorter doses in zones 4 and 5.
How does this differ from the simple 220-minus-age method?
The 220-minus-age method gives a single max HR estimate and computes zones as percentages of that max (e.g., 70% of max HR), without considering resting heart rate. The Karvonen method uses HRR (max HR minus resting HR) and is more accurate because it accounts for individual fitness. For two 35-year-olds with the same max HR (185 bpm) but different resting HR (60 vs 50), the Karvonen 70% target is 147.5 vs 144.5 bpm — close, but the difference grows at higher intensities and matters for elite training where zones must precisely target lactate and VO₂max regions.