Calculate all five heart rate training zones using the Karvonen formula. See your exact HR ranges, fat vs carb fuel ratios, calorie estimates, and zone-specific nutrition tips.
Measure first thing in the morning before getting up
Used to estimate calories burned per zone
Leave blank to use Tanaka formula (208 − 0.7 × age)
Now that you know your zones, dial in your nutrition with BiteKit. Track your pre- and post-workout meals effortlessly — just speak or type what you ate and let AI handle the rest.
Heart rate training zones divide exercise intensity into five bands based on your cardiovascular effort. Each zone produces distinct physiological adaptations, uses different fuel sources, and requires a different nutrition strategy. Training in the right zone for your goal — whether fat loss, endurance, or peak performance — is one of the most effective ways to optimize your results.
Unlike simple age-based formulas, the Karvonen formula used by this calculator personalizes your zones by incorporating your resting heart rate. This accounts for individual cardiovascular fitness and produces significantly more accurate zone boundaries.
The Karvonen method uses your Heart Rate Reserve (HRR) — the difference between your maximum and resting heart rates — as the foundation for calculating each zone.
Max HR = 208 − (0.7 × age)
More accurate than the traditional 220 − age, especially for adults over 40. Enter your known max HR to override this estimate.
HRR = Max HR − Resting HR
A higher HRR generally indicates better cardiovascular fitness.
Target HR = (HRR × intensity%) + Resting HR
Example (Zone 2, 60–70% HRR): For Max HR = 185, Resting HR = 62 → HRR = 123. Zone 2 = (123 × 0.60) + 62 = 136 bpm to (123 × 0.70) + 62 = 148 bpm.
Very light effort. Used for warm-ups, cool-downs, and active recovery between hard training days. Fuel is primarily fat (~85%). Promotes blood flow and removal of metabolic waste without adding training stress. Can be maintained for hours.
Light to moderate effort. The foundation of endurance training. Fat provides ~65% of fuel, making this the most efficient zone for improving fat oxidation. Zone 2 training improves mitochondrial density and metabolic efficiency. Fasted cardio works well here. Elite endurance athletes spend the majority of their training volume in Zone 2.
Moderate effort. The “comfortably hard” zone where carbohydrates begin to dominate (~55% carb, 45% fat). Improves cardiovascular efficiency and lactate clearance. Sustainable for 30–90 minutes depending on fitness. A light carb snack 30–60 minutes before will improve performance and recovery.
Hard effort. Above the lactate threshold — carbohydrates dominate at ~75%. Improves speed, power, and lactate tolerance. Can typically be sustained for 10–30 minutes at the lower end or as intervals of 2–8 minutes at the upper end. Fuel with fast-acting carbs (30–60 g/hr) for sessions lasting more than 45 minutes.
Maximum effort. Nearly all fuel comes from carbohydrates (~90%). Only sustainable for 30 seconds to 2 minutes per interval. The most powerful stimulus for increasing VO2 max and anaerobic power. Requires maximum carbohydrate availability — eat a full carb-rich meal 2–3 hours before, or a fast-acting carb snack 30 minutes prior. Protein intake post-workout is critical for muscle repair.
What you eat before, during, and after exercise should match the zone you're training in. Here's a practical nutrition guide for each zone:
| Zone | Pre-Workout | During | Post-Workout |
|---|---|---|---|
| Z1 Recovery | Fasted OK | Water | Normal meal |
| Z2 Fat Burn | Fasted or light protein | Water + electrolytes (1h+) | Protein + light carb |
| Z3 Aerobic | Light carb snack 30–60 min before | 30 g carb/hr (sessions over 60 min) | 3:1 carb-to-protein meal |
| Z4 Anaerobic | Full carb meal 2–3 hrs before | 30–60 g carb/hr | High protein + carb refuel |
| Z5 VO2 Max | Max carb load | Gel or fast carb as needed | Protein shake + carbs immediately |
For most athletes and fitness enthusiasts, an 80/20 approach is most effective: spend roughly 80% of training time in Zones 1–2 (low intensity) and 20% in Zones 3–5 (moderate to high intensity). This polarized model, used by elite endurance athletes, balances aerobic base building with high-intensity adaptations while minimizing recovery demands.
Easy runs, cycling, or swimming. Builds mitochondria, fat-burning efficiency, and aerobic capacity without excessive fatigue.
Tempo runs or sustained efforts. Raises your lactate threshold so you can sustain faster paces at lower heart rates.
Intervals and sprints. Improves VO2 max and anaerobic power. Limit to 1–2 sessions per week with adequate recovery between sessions.
Combine your heart rate zone data with these calculators for a complete training and nutrition picture:
Zone 1 (Recovery, 50–60% HRR) is for active recovery. Zone 2 (Fat Burn, 60–70% HRR) maximizes fat oxidation. Zone 3 (Aerobic, 70–80% HRR) builds cardiovascular efficiency. Zone 4 (Anaerobic, 80–90% HRR) develops speed and lactate threshold. Zone 5 (VO2 Max, 90–100% HRR) improves peak aerobic power through short, maximum-intensity intervals.
The Karvonen formula uses your Heart Rate Reserve (HRR = Max HR − Resting HR) to calculate target zones: Target HR = (HRR × intensity%) + Resting HR. This is more accurate than simple percentage-of-max-HR methods because it accounts for your individual resting heart rate, which reflects your personal cardiovascular fitness.
Measure your resting heart rate first thing in the morning before getting out of bed. Count your pulse for 60 seconds, or count for 30 seconds and multiply by 2. Average measurements over 3 mornings for accuracy. Normal range is 60–100 bpm; fit athletes often measure 40–60 bpm.
Tanaka formula: Max HR = 208 − (0.7 × age). This is more accurate than the traditional 220 − age formula, particularly for adults over 40. Research shows it has a standard error of ±10 bpm. For the most accurate zones, enter your actual max HR from a supervised stress test or a true all-out effort.
Zone 2 (60–70% HRR) has the highest percentage of calories from fat (~65%). Zone 1 is even higher percentage-wise (~85%) but total calorie burn is low. For maximum total fat burned, higher zones burn more calories overall despite a lower fat percentage. Zone 2 is best for improving your body's fat-burning efficiency long-term.
For Zone 3, have a light carb snack 30–60 minutes before. For Zone 4, eat a full carbohydrate meal 2–3 hours before or a fast-acting carb snack 30 minutes prior. For Zone 5 (VO2 Max intervals), maximize carbohydrate availability with a full pre-workout meal. After any session above Zone 2, prioritize 20–40 g of protein within 30–60 minutes to support muscle repair.
BiteKit makes it effortless to track what you eat before and after every workout. Just speak or type your meals — AI calculates the nutrition instantly.
Learn More About BiteKit