Heart rate zone calculator: max HR and zones

Zone	Heart rate range	Purpose
Zone 1	–	Very easy, active recovery, warm-up and cool-down
Zone 2	–	Aerobic base, long easy runs
Zone 3	–	Steady aerobic development
Zone 4	–	Tempo runs near the anaerobic threshold
Zone 5	–	Intervals, short hard efforts
Zone 1	–	Recovery
Zone 2	–	Aerobic base
Zone 3	–	Aerobic tempo
Zone 4	–	Near threshold
Zone 5a	–	At threshold
Zone 5b	–	Above threshold
Zone 5c	–	VO2max range

What max heart rate tells you

Maximum heart rate (HRmax) is the highest rate your heart reaches under maximal effort. It declines with age and varies between individuals. The most common estimate comes from Tanaka, Monahan and Seals: HRmax = 208 − 0.7 × age. At 35, that gives 208 − 24.5 = 183.5 beats per minute. The older, better-known rule of thumb from Fox is 220 − age, giving 185 at 35.

Both formulas are estimates from population studies, not an individual measurement. If you know your real max heart rate from a graded test or an all-out race, enter it directly to override the formula.

How the calculator works

With the "% HRmax" method, five zones are fixed percentage bands of max heart rate: 50–60%, 60–70%, 70–80%, 80–90% and 90–100%. At 183.5 beats per minute, zone 2 (60–70%) works out to 110 to 128 beats per minute.

The Karvonen method, after Karvonen et al. (1957), instead uses heart rate reserve (HRR), the gap between resting and max heart rate: HRR = HRmax − resting HR. Each zone boundary is resting HR + percentage × HRR. With a max of 183.5 and a resting rate of 60, HRR is 123.5. Zone 2 (60–70% HRR) then sits at 134 to 146 beats per minute, higher than the plain percentage method because a low resting rate counts for more.

The third method is based on lactate threshold heart rate (LTHR) after Joe Friel. Run a 30-minute solo time trial and note the average heart rate of the last 20 minutes as your LTHR. The running zones from Friel are then percentages of LTHR: zone 1 below 85%, zone 2 85–89%, zone 3 90–94%, zone 4 95–99%, zone 5a 100–102%, zone 5b 103–106%, zone 5c above 106%. With an LTHR of 165, zone 3 sits at 149 to 155 beats per minute.

Interpretation and limits of the method

Formula-based estimates like Tanaka or Fox scatter by roughly ±10 to 12 beats per minute between people of the same age, according to the underlying study. With an estimated max of 183, the real value could easily be 173 or 193. A max heart rate measured in a true all-out test always beats any formula.

Medication such as beta blockers lowers resting and exercise heart rate noticeably, sometimes by 20 to 30 beats per minute. Anyone on such medication should not rely on formula-based heart rate zones and should instead use perceived effort or medically supervised performance testing.

Worked example

A 35-year-old runner with a resting heart rate of 60 gets a max heart rate of 183.5 by Tanaka, or 185 by Fox. With the percentage method, zone 3 (70–80% HRmax) sits at 128 to 147 beats per minute. With Karvonen, using the same max and resting rate, zone 3 (70–80% HRR) sits at 146 to 159 beats per minute, noticeably higher because the low resting rate enlarges the reserve.

Frequently asked questions

Which formula is more accurate for max heart rate, Tanaka or Fox?

Tanaka (208 − 0.7 × age) comes from a larger, more recent meta-analysis (Tanaka, Monahan & Seals 2001) and is now the more widely used estimate. Fox (220 − age) is older and tends to overestimate max heart rate in older people. Both fall within the ±10 to 12 beat scatter, so a measured value beats either.

What is the difference between % HRmax and Karvonen?

The percentage method uses plain fractions of max heart rate without accounting for resting heart rate. Karvonen factors in resting heart rate via heart rate reserve, which shifts zones upward, especially for well-trained people with a low resting rate. At a max of 183.5 and a resting rate of 60, Karvonen puts zone 2 at 134 to 146, versus just 110 to 128 with the plain percentage method.

How do I find my lactate threshold heart rate for the Friel method?

Following Joe Friel, run a 30-minute solo time trial at a consistently hard effort, mark a lap at 10 minutes, and take the average heart rate of the final 20 minutes as an approximation of your LTHR.

Why are the zones unreliable if I take beta blockers?

Beta blockers directly lower resting and exercise heart rate regardless of fitness. Formulas like Tanaka, Fox and Karvonen all assume an unmedicated heart rate, so every calculated zone shifts out of line when you are on such medication.

Is a heart rate watch enough to stick to these zones in training?

Yes, a chest strap or optical heart rate watch is enough to monitor the calculated ranges during training. Sticking to the same method consistently over several weeks matters more than the exact formula, so your training load stays comparable over time.