Target Heart Rate Calculator
Find your training heart-rate zones using the Karvonen formula.
Inputs
Allowed range: 10 to 100
Allowed range: 30 to 120
Results
How it works
We estimate maximum heart rate as HRmax = 220 − age, then apply the Karvonen reserve method: THR = (HRmax − HRrest) × intensity + HRrest. Zones use 50–60% (warm-up), 60–70% (fat-burn / easy), 70–80% (aerobic), 80–90% (threshold), 90–100% (max).
Complete guide
Target heart rate is the bpm window where your cardiovascular system gets the specific training stimulus you want — easy recovery, fat oxidation, aerobic base, lactate threshold, or VO₂max. Training inside a defined zone is more reproducible than training by feel, and over weeks it produces measurably better fitness gains than random-effort sessions.
This calculator uses the Karvonen heart-rate-reserve method, considered more accurate than a flat percentage of max heart rate because it accounts for your resting heart rate (a proxy for cardiovascular efficiency). The formula is THR = (HRmax − HRrest) × intensity + HRrest, with HRmax estimated as 220 − age. A fit person with a low resting heart rate will get higher zone bpm values than an unfit person of the same age, reflecting their larger 'working' reserve.
How to use it: measure your resting heart rate first thing in the morning before getting out of bed (an average of 3 mornings is best). Enter your age and that resting value. The calculator returns your estimated max HR, your heart-rate reserve, and the bpm range for each of the five training zones.
Worked example: a 30-year-old with a resting heart rate of 65 bpm has an estimated HRmax of 190 and a reserve of 125. Zone 2 (60–70%) lands at roughly 140–153 bpm — the classic 'conversational pace' for long endurance runs. Zone 4 (80–90%) is about 165–178 bpm — the threshold range used for 20-minute tempo intervals.
Practical training prescription: spend 70–80% of weekly training time in Zone 1–2 to build an aerobic base (the so-called 'polarized' or '80/20' model used by elite endurance athletes). Use Zone 3 sparingly — it is fatiguing without providing the unique benefit of either easier or harder work. Reserve Zone 4 for once-a-week threshold sessions and Zone 5 for brief VO₂max intervals (3–5 minutes at a time, with full recovery).
Caveats: the 220 − age formula has roughly ±10–12 bpm of individual variation. If you have a heart-rate monitor and can perform a hard 5K or 20-minute time trial, your peak HR during that effort is a much better personal max. Beta-blockers, dehydration, heat, caffeine, and altitude all shift heart-rate response — recalibrate when conditions change.
Frequently asked questions
- How accurate is the 220 − age formula?
- It is a population-average estimate with roughly ±10–12 bpm of individual variation. Newer formulas like Tanaka's 208 − 0.7 × age fit older adults a bit better. For training precision, a field test (a hard 5K, a 20-minute time trial, or a graded treadmill test) gives a personal max you can trust.
- Why use the Karvonen formula instead of plain % of max?
- Because two people with the same HRmax but very different resting heart rates have different cardiovascular reserves. Karvonen scales intensity to that reserve, so the resulting zones better match perceived effort and metabolic load. Most sports-science programs use Karvonen for this reason.
- What is the difference between Zone 2 and 'fat-burning zone'?
- They are essentially the same — 60–70% of heart-rate reserve, where the body primarily uses fat as fuel. The label 'fat-burning zone' is marketing; the underlying physiology is just steady-state aerobic work. Total calories matter more than fuel mix for weight loss, but Zone 2 is also the most repeatable, lowest-stress training intensity, which is why endurance coaches lean on it heavily.
- Should beginners train in higher zones?
- No. Beginners get the largest fitness gains from accumulated Zone 1–2 time, with maybe one weekly higher-intensity session once a base is built. Skipping straight to Zone 4–5 work tends to produce injury and burnout rather than fitness.
- How does resting heart rate change with fitness?
- It typically falls as cardiovascular fitness improves — well-trained endurance athletes often sit in the 40s or low 50s. Recalculate your zones every few months if your resting HR drops more than 5 bpm.