Free tool
Zone 2 heart rate calculator
Zone 2 is the easy cardio that keeps showing up in the healthy-aging research. Here is a rough range for your age, plus the test that beats any number.
Your rough Zone 2 range
Beats per minute, give or take. This uses the simple 220-minus-age estimate, so treat it as a starting point, not a rule.
The test that beats the number: you should be able to hold a conversation but not sing. If you can chat easily, nudge up. If you cannot get a sentence out, slow down. The talk test is more reliable than any formula.