Heart Rate Zone Calculator

"220 minus your age" is the heart rate formula everyone's gym trainer has said at some point, and it's also just... not very good. It was derived decades ago from a small, non-systematic review of a handful of studies, and it consistently overestimates max HR for older adults and underestimates it for some younger ones. I kept it in this calculator because people expect to see it, but I built in Tanaka and Karvonen specifically so it's not the only option.

How it works

220−age just subtracts your age from 220, no other inputs. Tanaka's formula (208 − 0.7 × age) was derived from a much larger meta-analysis and tracks actual measured max heart rates more closely, especially past age 40 — it produces a noticeably higher number for older users, which is usually more realistic, not less safe. Karvonen goes a step further and factors in your resting heart rate (measured first thing in the morning, before you get up) using heart-rate reserve: (max − resting) × zone% + resting. Because it accounts for your actual cardiovascular fitness rather than just your age, two people the same age with different resting heart rates get meaningfully different zone boundaries from Karvonen, even though 220-age would give them identical numbers.

A real example

Take a 45-year-old with a resting heart rate of 58 bpm. 220−age gives a max HR of 175. Tanaka gives 208 − (0.7×45) = 176.5 — close enough that it barely matters here. But look at Zone 2 (60-70%, the "conversational pace" endurance zone): the simple max-HR method puts it at roughly 105-123 bpm. Karvonen, using that same 176.5 max and the 58 resting HR, puts Zone 2 at 129-141 bpm — a meaningfully higher and narrower range. For someone with a genuinely low resting heart rate from being reasonably fit already, Karvonen's zones sit higher because their heart has more reserve to work with.

Common mistakes

• Using Karvonen with a resting heart rate you guessed instead of measured. The whole benefit of Karvonen comes from an accurate resting HR. Take it lying down, right after waking up, before coffee or checking your phone — not a number you remember from a wearable's daily average, which tends to run higher than true resting.
• Spending most training time in Zone 4-5 because it "feels like it's working." Most structured endurance programs put 70-80% of total training time in Zone 1-2, not because those zones are more important, but because that's what builds the aerobic base the harder sessions depend on. If every session feels hard, you're probably not actually training zones, you're just training hard all the time.
• Treating any of these formulas as a substitute for a real max-HR test if you have a heart condition. All three methods here are population estimates. If you have a cardiac history or you're starting exercise after a long break, get a supervised test instead of trusting a formula on a fitness calculator.