Cardio Heart Rate Zones

“Cardio” in American guideline language is not one zone but two bands: moderate intensity at about 50 to 70% of maximum heart rate, and vigorous at about 70 to 85%. Everything a public health recommendation asks of you fits inside that 50 to 85% target span. Enter your age below to see it in beats per minute, with zone 3 — the middle of the aerobic range — highlighted.

The AHA bands next to the five-zone display

AHA band	% of max HR	Where it lands on the calculator
Moderate intensity	50–70%	Zones 1 and 2
Vigorous intensity	70–85%	Zone 3 and the lower part of zone 4
Above the charted target	over 85%	Upper zone 4 and all of zone 5

The five-band display is a coaching convention that slices the same span more finely; the AHA’s target zone chart simply stops at 85%. Neither is a contradiction, but it explains why a watch can report “zone 5” for something no public health document has an opinion about.

If you want a printed lookup instead of a calculator — every age against every zone in bpm — the target heart rate for exercise chart is laid out that way.

Turning bands into a week

This is where cardio zones actually earn their keep, because the guideline is written in minutes, not beats:

• At least 150 minutes a week of moderate activity, or 75 minutes of vigorous, or a combination — vigorous minutes count roughly double.
• Up to 300 minutes a week buys additional benefit.
• Muscle-strengthening work on at least 2 days a week, which heart rate zones say nothing about and which the same recommendation treats as non-optional.
• Sit less. Even light activity offsets some of the risk of being sedentary.

A workable shape: three 40-minute sessions mostly in the moderate band, one shorter session that climbs into the vigorous band, and two strength days. That clears 150 minutes with room to spare and does not require living in zone 3.

Building a single cardio session

Start in zone 1 for five to ten minutes, spend the main block in zone 3, and come back down to zone 1 to finish. The mistake to avoid is starting too fast: heart rate lags effort by a minute or two, so the first stretch feels easy on the monitor even when you have already overcooked it, and you pay for it at minute 25.

If you train without a device, the AHA’s own description of moderate intensity is the test — your heart beats faster and you breathe harder than normal, but you can still talk. Lose the ability to hold a sentence and you have crossed into vigorous.

The fat loss question, briefly

“Cardio heart rate zones for fat loss” is a search that assumes a zone decides the outcome. It does not. Lower intensities draw a larger fraction of their energy from fat, higher intensities burn more calories in the same time, and body weight responds to the weekly total against what you eat. The full version of that argument, with the comparison table, is on fat burning heart rate zone, and the practical week-planning version is on the weight loss heart rate calculator.

The genuinely useful zone rule for fat loss is the boring one: pick an intensity you will still be doing in three months.

This content is informational and does not replace guidance from an exercise professional. See the max heart rate calculator for the number all these percentages are taken from, and the heart rate zone calculator for the full five-band breakdown.