What Is a Heart Rate Zone?
Every workout lives somewhere on a scale of intensity, and heart rate is the most practical way to measure it. Trainers divide that scale into five zones: Zone 1 is a light warm up, Zone 2 builds your aerobic base and burns a high share of fat, Zone 3 improves cardiovascular fitness, Zone 4 builds speed and lactate threshold, and Zone 5 is all out effort for short bursts.
On a bad sleep night an easy pace can feel brutally hard, while on a great day you might cruise without realizing you are undertraining. Zones remove the guesswork. Fat loss means Zone 2. A faster 5K means Zone 4 intervals. Knowing your numbers turns every session into a plan instead of a gamble.
The Karvonen Method: Why It Beats 220 Minus Age
The basic method applies percentages to your max, but treats a fit runner and a beginner of the same age as identical. Karvonen folds in your resting heart rate through heart rate reserve, the gap between max and resting rate. At 55 resting bpm a fit person has a bigger reserve than a beginner at 75, so the same 70% effort lands at a different bpm for each.
The formula is: target heart rate = [(MHR - RHR) x intensity] + RHR. Worked example for a 35 year old with a resting heart rate of 62 bpm, using the Tanaka formula:
| Step | Math | Result |
| Max heart rate (Tanaka) | 208 - (0.7 x 35) | 184 bpm |
| Heart rate reserve | 184 - 62 | 122 bpm |
| Zone 3 low end (70%) | (122 x 0.70) + 62 | 147 bpm |
| Zone 3 high end (80%) | (122 x 0.80) + 62 | 160 bpm |
So this runner's aerobic Zone 3 runs from 147 to 160 bpm. Without Karvonen, plain 70% of 184 would start Zone 3 at 129 bpm, a full 18 beats too low for someone this fit. The basic method tends to hold trained athletes back, which is why Karvonen is the default here. To see how those steady Zone 2 sessions translate into calories, our calorie calculator estimates burn for hundreds of activities.
Max Heart Rate Formulas Compared
Every zone starts with an estimate of max heart rate, since true max needs a supervised test. This calculator offers four formulas:
| Formula | Math | Best for |
| Standard | 220 - age | Quick estimates, general use |
| Tanaka | 208 - (0.7 x age) | Most adults, better age fit |
| Gulati | 206 - (0.88 x age) | Women, based on female athletes |
| Measured | Your own tested value | Most accurate, if you have one |
The standard 220 minus age formula dates to the 1970s and can miss by 10 to 20 bpm. Tanaka, built from a meta analysis of over 18,000 subjects, tracks age related decline better and is the sensible default. Gulati was developed for women after researchers found the standard formula overestimates female max heart rates. If you have a lab stress test result or a verified field test on a chest strap, choose Measured, since a real measurement beats every formula.
The Five Zones and What to Do in Each
| Zone | Intensity | Purpose | Try this |
| Zone 1: Recovery | 50 - 60% | Warm up, cool down, active recovery | Easy walk, gentle yoga, slow cycling |
| Zone 2: Fat burn | 60 - 70% | Build aerobic base, high fat share of fuel | Brisk walk, easy jog, steady bike |
| Zone 3: Aerobic | 70 - 80% | Improve cardiovascular fitness | Running, swimming, rowing |
| Zone 4: Anaerobic | 80 - 90% | Raise lactate threshold, build speed | Tempo runs, hill repeats |
| Zone 5: VO2 max | 90 - 100% | Maximal speed and power | Sprint intervals, HIIT bursts |
Most weekly training should sit in Zones 1 through 3. Coaches often aim for roughly 80% of volume easy and 20% hard: easy volume builds the engine, hard sessions sharpen it. Zone 5 means short intervals with full recovery, not a 40 minute grind. Pairing steady Zone 2 work with a quick look at your BMI calculator result can help you track the body composition side of progress.
Pick the Right Zone for Your Goal
Fat loss means Zone 2: at 60 to 70% of max your body leans on fat for fuel, and the intensity holds for 45 minutes or more. Endurance means Zone 3 over a Zone 2 base. Speed means Zone 4 intervals to raise your lactate threshold. Recovery means Zone 1 only: a walk or easy spin that boosts blood flow without training stress.
Avoid training in the gray middle, around the top of Zone 3, for everything. It is too intense to recover from easily and too easy to build real speed. Heat, dehydration, stress, caffeine, and poor sleep all raise heart rate, so a Zone 2 run on a hot afternoon may read like Zone 3. Recheck your resting heart rate every few months: a falling resting rate means your zones need recalculating.
How to Use This Calculator
Enter your age and resting heart rate (best measured first thing in the morning, after five minutes of stillness, averaged over three days). Choose a max heart rate formula (Tanaka is a solid default, Gulati for women), or Measured if you have a tested value. Pick the basic or Karvonen method, select your goal, and your five zones appear with bpm ranges, workout picks, and a visual zone bar. Recovery is half the formula, so plan your rest with our sleep cycle calculator too. These zones are designed for adults, so treat the numbers as a loose guide if you are under 20.
These are estimates, not medical measurements. Formula based max heart rates can be off by 10 to 20 bpm, and medications like beta blockers change your response. If you have a heart condition, chest pain, dizziness, or take heart medication, talk to your doctor before training by heart rate, especially in Zones 4 and 5.
Frequently Asked Questions
What is the Karvonen method for heart rate zones?
It personalizes zones using your resting heart rate: target = [(max - resting) x intensity] + resting. It beats plain percentages of max, especially for fit people whose low resting rates shift zones upward.
Which heart rate zone burns the most fat?
Zone 2 (60 to 70% of max) gets the "fat burn" label because fat supplies the biggest share of fuel there. But higher zones burn more total calories per minute, so session length and diet matter too.
Is 220 minus age accurate for max heart rate?
Only roughly. It can miss your true max by 10 to 20 bpm. Tanaka (208 minus 0.7 x age) fits most adults better, and a supervised test is the gold standard.
How do I measure my resting heart rate?
Sit or lie still for five minutes, then count your pulse for 60 seconds or glance at a fitness tracker. The best reading comes first thing in the morning. Repeat for three days and take the lowest.
Is it safe to exercise in Zone 5?
For healthy, conditioned adults, short Zone 5 intervals with full recovery are normal training. Beginners should build a Zone 2 and 3 base first, and anyone with heart issues should get medical clearance before going all out.