What heart rate zone should you be training in?

Why this gives higher numbers than the chart on the treadmill

Most gym charts take a percentage of maximum heart rate directly. This calculator uses the Karvonen method, which works from heart rate reserve — the gap between your maximum and your resting rate — and adds the result back to your resting rate.

The two disagree substantially. For a 35-year-old with a resting rate of 70, maximum heart rate is 185 and reserve is 115. A "70% effort" target comes out as:

• Plain percentage of max: 185 × 70% = 130 bpm
• Karvonen: 70 + (70% × 115) = 151 bpm

A 21 bpm gap is the difference between a session that feels like walking and one that feels like training. Karvonen is the better model because it accounts for the fact that your heart is already beating at 70 before you start — the effort you can actually vary is the reserve above that, not the whole range from zero.

This also means a fitter person, whose resting rate has dropped, gets different targets from the same formula. That is the intended behaviour: as conditioning improves and resting rate falls, reserve widens and the zones move.

The five zones for a 35-year-old resting at 70

• Zone 1, 50–60% — 128 to 139 bpm. Warm-up and recovery. Conversational throughout.
• Zone 2, 60–70% — 139 to 151 bpm. The endurance zone, where most training volume should sit. You can speak in full sentences.
• Zone 3, 70–80% — 151 to 162 bpm. Aerobic. Speech becomes short phrases.
• Zone 4, 80–90% — 162 to 174 bpm. Threshold. Sustainable for perhaps an hour by trained athletes, far less by everyone else.
• Zone 5, 90–100% — 174 to 185 bpm. Maximal, tolerable in intervals of minutes.

The common error is spending most sessions in zone 3 — hard enough to accumulate fatigue, not hard enough to drive adaptation, and too hard to allow recovery. Most endurance programmes put the bulk of training in zone 2 and a small share in zones 4 to 5.

Two honest limits on the arithmetic

The 220-minus-age estimate for maximum heart rate is a population average with a wide spread — individual maxima commonly sit 10 to 20 beats either side of it, so a genuine 35-year-old maximum might be 165 or 205. Every zone here inherits that uncertainty. If your perceived effort consistently disagrees with the numbers, trust your body and consider a supervised maximum test rather than adjusting your training to fit the formula.

Resting heart rate has to be measured properly to be useful: taken on waking, before getting out of bed, before caffeine, ideally averaged over several mornings. A figure taken mid-afternoon at a desk is typically 10 to 15 beats high and will push every zone up with it.

These are general fitness estimates, not medical guidance. Beta blockers and several other common medications suppress heart rate directly and make every number here meaningless — if you take one, or have any cardiac condition, get your zones from your doctor rather than from a formula.

Common questions

What is the Karvonen formula and why use resting heart rate?

The Karvonen formula calculates a heart rate reserve (max heart rate minus resting heart rate) and applies intensity percentages to that reserve, then adds resting heart rate back: target = resting + intensity% × (max − resting). Because it factors in your resting rate, it accounts for individual fitness differences better than applying a percentage to max heart rate alone — two people with the same max heart rate but very different resting rates will get meaningfully different target zones.

What heart rate zone should I train in?

It depends on your goal — lighter zones (50-70%) suit recovery, warm-ups, and base aerobic building, while higher zones (70-90%) build cardiovascular capacity, speed, and race-pace fitness. Most structured training plans mix zones across a week rather than staying in one permanently. This isn't personalized medical or coaching guidance, so factor in how you actually feel during a session too, not just the number on a monitor.

How do I find my resting heart rate?

Measure your pulse first thing in the morning, before getting out of bed and before caffeine, for the most accurate reading — count beats for a full 60 seconds, or 30 seconds and double it, ideally averaged over a few mornings. Many fitness trackers and smartwatches also estimate this automatically overnight from continuous heart rate monitoring.

Is 220 minus age accurate for everyone?

It's a population average with a meaningful margin of error for any given individual — plus or minus 10-15 beats per minute isn't unusual, meaning some people's true max heart rate is noticeably higher or lower than the formula predicts. It remains a useful starting estimate for most people without access to lab testing, but a supervised maximal exercise test is more accurate if precision genuinely matters for your training.

Worked example: a 35-year-old with a resting heart rate of 70 bpm: max heart rate = 220 − 35 = 185 bpm; heart rate reserve = 185 − 70 = 115 bpm. Fat Burn zone (60-70%) = 70 + 0.60×115 to 70 + 0.70×115 = 139 to 150.5, or roughly 139-151 bpm. Peak zone (80-90%) = 70 + 0.80×115 to 70 + 0.90×115 = 162 to 173.5, or roughly 162-174 bpm.