Target heart rate calculator

Heart-rate zones help you keep easy days easy and hard days purposeful. This free calculator estimates maximum heart rate with the Tanaka equation (208 − 0.7×age), then builds warm-up, fat-burn, cardio, and peak ranges. Enter resting heart rate to switch to Karvonen heart-rate reserve math.

Tanaka max HR versus older rules of thumb

Many people still hear “220 minus age.” Tanaka’s 208 − 0.7×age often fits adult data better and tends to be less aggressive for middle-aged athletes. Example: at age 30, Tanaka max HR is about 187 bpm. Zones are then percentages of that max—or of heart-rate reserve if you supply resting HR.

Resting heart rate is best taken seated after waking, before caffeine. Values around 40–80 bpm are common depending on fitness and genetics; the tool accepts a practical adult range and ignores implausible entries. If resting HR is blank, zones use simple percentages of Tanaka max HR.

What the four zones are for

Warm-up (about 50–60%) is for priming and recovery spins. Fat-burn (60–70%) is conversational aerobic work—useful for base building, not a magic fat-only switch. Cardio (70–80%) is harder sustained effort. Peak (80–90%) covers intervals and races where you should already have a base and a reason to go hard.

Heart rate lags behind sudden pace changes, so short hills may spike effort before the watch catches up. Use zones as lanes, not handcuffs. Perceived exertion and pace still matter, especially in heat, dehydration, or when medications alter heart-rate response.

Karvonen when you know resting HR

Karvonen intensity = (max HR − resting HR) × percent + resting HR. Fitter people with lower resting rates get slightly different zone boundaries than percent-of-max alone. If your easy runs always feel too hard at “60% of max,” try Karvonen with a measured resting value.

Recheck resting HR after illness, overreaching, or a big fitness jump. An elevated morning pulse can signal incomplete recovery even when the calendar says you are ready for intervals.

Training, fueling, and honesty

Most weekly minutes should stay easier than peak. Stacking every session in the top zones is a fast path to flat performance. Pair hard days with carbohydrates and total calories from a realistic TDEE, and keep protein steady for repair.

Chest pain, dizziness, unexplained breathlessness, or known heart disease are stop signs—not zone puzzles. This calculator is educational, not a stress test or medical clearance. FreeNutri provides it free without signup so you can sketch zones, then train with common sense.

Devices and drift

Optical wrist sensors vary with fit, skin tone, tattoos, and motion. Chest straps are often steadier for intervals. If zone numbers and how you feel diverge chronically, trust a field test with a coach or clinician rather than only age formulas.

Age-predicted max HR has individual error. Some athletes exceed or undershoot Tanaka estimates. Use the ranges to organize intent; update them when race data or supervised testing gives a better personal max.