Heart Rate Zone Calculator
Z1 to Z5 · % HRmax & Karvonen · Age Estimate · Pace → Zone · HYROX Context
Training without knowing your heart rate zones is like navigating without a compass. Too many athletes spend most of their training volume in Zone 3 - the 'comfortably hard' intensity - while maximum aerobic development happens in Zone 2, and peak power in Zone 5. Knowing your zones means knowing exactly what intensity to run at for every session.
This tool offers two calculation methods: simple percentage of HRmax (quick and widely used) and the Karvonen method based on heart rate reserve (HRmax − resting HR), recognized as more accurate - especially for trained athletes with a low resting heart rate. If you know your resting HR, use Karvonen.
HYROX context is built into every zone: what intensity should you target on the 8 running segments? On which stations do you end up in Zone 5 without meaning to? This information turns heart rate zones into a genuine fitness racing training plan.
Related guide
Preparing Your First Hyrox®: the Complete Guide12-week programme, equipment, nutrition, race day tipsFrequently Asked Questions about Heart Rate Zones
What are the 5 heart rate zones?+
The 5 training zones are: Z1 Recovery (50-60% HRmax), Z2 Base Endurance (60-70%), Z3 Tempo (70-80%), Z4 Lactate Threshold (80-90%) and Z5 VO₂max/Sprint (90-100%). Each zone targets different energy systems and produces distinct physiological adaptations.
What is the difference between % HRmax and the Karvonen method?+
The % HRmax method applies the percentage directly to your maximum heart rate. The Karvonen method (HR reserve) uses the formula: zone = resting HR + (HR reserve × %). It is more accurate because it accounts for your resting HR - an athlete with a resting HR of 40 bpm has a different working range than someone at 70 bpm, even with the same HRmax.
How do I accurately measure my HRmax?+
Age-based estimates (220-age, Tanaka, Gellish) give approximate values with a ±10-15 bpm margin of error. For an accurate measurement, perform a progressive effort test to exhaustion (Cooper protocol, lab treadmill test, or a full sprint finish in competition). HRmax varies very little day to day once physical maturity is reached.
What heart rate zone should I target in HYROX?+
In HYROX, the 8 running segments should ideally be run in Zone 2-3 for intermediate to advanced athletes. Short stations like Sled Push or Burpee Broad Jumps will push you into Zone 4-5 - that's normal and unavoidable. The goal is to recover quickly back to Zone 2-3 on the next running segment.
What is Zone 2 and why is it so important?+
Zone 2 (60-70% HRmax, moderate effort, conversation possible) is the base endurance zone. It develops mitochondrial density, improves fat oxidation, and increases stroke volume. Elite endurance athletes perform 70-80% of their weekly volume in Zone 2. It is the foundation on which all aerobic performance is built - HYROX included.
How much time should I spend training in Zone 2 per week?+
The general recommendation is to dedicate 70-80% of your weekly training volume to Zone 2. For an athlete training 6-8 hours per week, that's roughly 4-6 hours in Zone 2. Practically, one long Zone 2 run of 60-90 minutes plus 2-3 short 30-45 minute sessions provides a solid aerobic base for improving your endurance and HYROX performance.
How do I stay in Zone 2 when it feels too easy?+
Many athletes naturally run too fast and drift into Zone 3. To stay in Zone 2, monitor your heart rate in real time (GPS watch with heart rate monitor) and don't hesitate to walk if needed. The "talk test" is a simple guide: you should be able to speak in full sentences without breathlessness. The first few weeks, Zone 2 can feel frustratingly slow - that's normal, and it improves quickly as your aerobic base develops.