Why does the Karvonen formula need my resting heart rate?

It computes zones from your heart rate reserve (HRmax minus resting HR), so two people of the same age with different fitness get different, more personal zones.

Is the fat burning zone the best zone for weight loss?

Not necessarily. Zone 2 burns the highest share of fat, but higher zones burn more total calories per minute. The best zone for weight loss is the one you can sustain consistently within a calorie deficit.

How should I measure resting heart rate?

Right after waking, before coffee or getting up: sit or lie still and count your pulse for 60 seconds, or average a few mornings from a wearable.

Target Heart Rate & Karvonen Formula Guide

Heart rate zones turn a vague instruction like "train harder" into a number you can see on a watch. This guide explains where the zones come from, why the Karvonen formula beats simple percentages, and what each zone is actually good for — so the table the target heart rate calculator gives you becomes a training plan instead of trivia.

Open Target Heart Rate Calculator

Step 1: Maximum Heart Rate

Every zone system starts from HRmax. The classic estimate is 220 − age; the Tanaka formula (208 − 0.7 × age) fits research data better, especially past age 40 — at 60 it predicts 166 bpm versus the classic 160. Both are population averages with real individual spread, so if you have ever seen a higher number on a hard race finish, trust the measured value and enter it directly.

Step 2: The Karvonen Formula

Simple %HRmax zones ignore fitness. The Karvonen method fixes that by working from your heart rate reserve — the span between resting and maximum:

Target HR = (HRmax − resting HR) × intensity + resting HR

Example: age 30, resting 60. HRmax ≈ 190, reserve = 130. The 70% point is 130 × 0.7 + 60 = 151 bpm. A fitter person with resting 50 gets 148 bpm for the same 70% — the formula automatically respects the difference. Measure resting HR right after waking: 60 seconds of counting, or a few mornings averaged from a wearable.

The Five Zones

Zone	Intensity	Feels like	Best for
Z1 Very Light	50–60%	Easy movement, full conversation	Warm-up, recovery days
Z2 Light	60–70%	Comfortable, can talk in sentences	Fat-burn share, endurance base
Z3 Moderate	70–80%	Working, short phrases only	Aerobic fitness
Z4 Hard	80–90%	Hard, a few words at most	Threshold, speed
Z5 Maximum	90–100%	All-out, unsustainable	Short intervals only

The Fat-Burn Zone, Without the Myth

Zone 2 earns its "fat burning" name because at that intensity the largest share of fuel comes from fat. It does not mean Zone 2 burns the most fat per workout — a Zone 4 session can burn more total calories, including fat, in the same time. For body-weight change, the calorie deficit does the work (see TDEE for weight loss); zones decide how sustainable and repeatable the training is. That is exactly why Zone 2 matters: it accumulates volume without wearing you down.

A Simple Weekly Pattern

Most sessions in Zone 2 — the 80% of the classic 80/20 endurance split.
One steady Zone 3 session when you want a bit more stimulus.
One or two interval sessions touching Zone 4–5, never on consecutive days.
Recheck your zones every few months — resting HR falls as fitness improves, and Karvonen zones shift with it.

Formula zones assume a healthy heart responding normally to exercise. Medication that alters heart rate (beta blockers in particular) or any cardiac condition means formula-based zones do not apply — get zones from a clinician or supervised test instead.

TDEE Calculator Guide, Weight Loss Calorie Guide, BMI Calculator Guide

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