Heart Rate Zones Calculator
Calculate your 5 heart rate training zones using the Karvonen (heart rate reserve) formula.
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How to use this calculator
The Karvonen formula uses Heart Rate Reserve (HRR = MaxHR − RestingHR) to calculate training zones. This accounts for individual fitness level better than pure percentage of max HR. Zone 1=50–60%, 2=60–70%, 3=70–80%, 4=80–90%, 5=90–100% of HRR.
- 1
Choose whether to use an age-predicted max HR or enter your own measured max HR.
- 2
If age-based, enter your age. If custom, enter the highest HR you've ever recorded in a hard effort.
- 3
Enter your resting heart rate (measure it in the morning before getting out of bed).
- 4
Use the five zones to structure your training sessions appropriately.
Frequently asked questions
What is the Karvonen formula?
The Karvonen formula calculates training zones using Heart Rate Reserve (HRR = MaxHR − RestingHR) rather than just a percentage of max HR. This makes zones more personalised because a fit person with a low resting HR gets different zone boundaries than a sedentary person with the same max HR.
How do I find my true max heart rate?
Age-predicted max HR (220 − age) is a population average with significant individual variation. A more accurate max HR can be found through a graded exercise test, or informally by recording your HR at the end of a maximal all-out effort (e.g., the last sprint in a hard interval session).
What should I train in each zone?
Zone 1–2 is used for easy recovery and base aerobic runs (most of your training volume). Zone 3 is moderate aerobic work. Zone 4 is lactate threshold training (tempo runs, intervals). Zone 5 is VO2 max work (short, hard intervals). Most endurance training plans follow an 80/20 split: 80% in Zones 1–2, 20% in Zones 4–5.
What resting heart rate should I enter?
Measure your resting HR first thing in the morning before getting out of bed. Lie still for a minute and count beats for 60 seconds. For most adults it is 60–80 bpm; well-trained endurance athletes may be in the 40–55 bpm range.
Heart Rate Training Zones Calculator
Why Training in Zones Works
Heart rate zones allow you to match workout intensity to your training goal. Easy aerobic runs in Zone 2 build mitochondrial density and fat-burning capacity without accumulating excessive fatigue. Threshold work in Zone 4 raises your lactate threshold — the pace you can sustain for about an hour. VO2 max intervals in Zone 5 develop cardiovascular capacity. Mixing these zones intelligently is the foundation of most structured training programmes.
Karvonen vs Simple Percentage Methods
Many basic zone calculators simply multiply max HR by a percentage. The Karvonen method subtracts resting HR first, then applies the percentage to the heart rate reserve, then adds resting HR back. This is more accurate because it normalises for cardiovascular fitness: two people with the same max HR but different resting HRs (one sedentary, one trained) should not train at the same absolute heart rate for the same physiological effect.
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