Heart Rate Zones

Enter your age and resting heart rate, and Heart Rate Zones hands you five precise training zones calculated using the Karvonen method — the formula that factors in your actual fitness level rather than treating everyone the same. You'll see exact beats-per-minute ranges for fat burn, aerobic base, anaerobic threshold, and peak effort, so you know exactly how hard to push during any session.

That gap between "working out" and training with intent usually comes down to knowing your numbers. Too many people grind away in the same middle zone, missing both the recovery benefits of easy effort and the adaptation that comes from briefly touching the red. Targeted zone work is the foundation of most structured health and fitness programming for good reason.

If you're pairing zone training with interval work, HIIT Timer makes a natural companion for keeping your rest-to-work ratios honest. Heart Rate Zones itself is a calculator, not a tracker — you'll want a chest strap or wrist sensor on hand to confirm you're actually hitting the ranges it gives you.