What heart rate zones are
Heart rate zones split the range between rest and maximum into bands that each match a training purpose. Working in the right band keeps easy days easy and hard days hard, which is the balance most endurance plans are built around. Instead of guessing effort, you watch a number.
This calculator uses five zones, from very light recovery in Zone 1 up to near-maximum work in Zone 5. The bpm you see for each depends on both your maximum and your resting heart rate.
The Karvonen heart-rate-reserve method
Many charts set zones as a flat percentage of maximum heart rate. This tool uses the Karvonen method instead, described by Karvonen, Kentala, and Mustala in 1957. It works from your heart-rate reserve, which is maximum heart rate minus resting heart rate:
- Heart-rate reserve = maximum heart rate − resting heart rate
- Target heart rate = resting heart rate + intensity × heart-rate reserve
Because the resting rate feeds into every zone, two people with the same maximum but different resting rates get different targets. The maximum itself comes from the Tanaka formula, 208 − 0.7 × age (Tanaka, Monahan, and Seals, 2001), unless you enter a measured value.
The five training zones
The table below lists each zone as a share of heart-rate reserve. The bpm ranges in the calculator above are these percentages applied to your own numbers.
| Zone | % of reserve | Feels like |
|---|---|---|
| Zone 1 — very light | 50 – 60% | Recovery, easy to chat |
| Zone 2 — light | 60 – 70% | Aerobic base, conversational |
| Zone 3 — moderate | 70 – 80% | Steady, talking gets harder |
| Zone 4 — hard | 80 – 90% | Threshold, short phrases only |
| Zone 5 — maximum | 90 – 100% | Near all-out intervals |
Using zones in training
A common pattern is to spend most of the week in Zones 1 and 2, add some Zone 3 to 4 work, and keep Zone 5 for short intervals. Recalculate your zones whenever your resting heart rate shifts, since a fitter heart usually rests slower. For the ceiling behind these numbers, see the max heart rate calculator, and to gauge aerobic fitness try the VO2 max calculator. To match a session with fuel, the running calorie calculator estimates what a run costs in calories.
