Health Formula • Published on July 30, 2026 • Last updated July 30, 2026
Tap a star to rate us instantly.
Age in years
Estimated Maximum Heart Rate in beats per minute (bpm)
Resting heart rate in bpm, measured first thing in the morning before getting up
Desired training intensity as a decimal, typically 0.5-0.85 (50%-85%) for aerobic training zones
Calculating a target heart rate training zone actually involves two separate decisions: which formula to use for estimating Maximum Heart Rate (MHR), and then how to convert that MHR into an actual target zone. Haskell & Fox's "220 minus age" is the older, simpler, and most widely recognized MHR formula, but it was derived from a relatively small and non-representative sample.
Tanaka's formula (208 − 0.7×age) is a more recent, research-validated alternative developed from a meta-analysis of a much larger dataset, and tends to be considered more accurate, particularly for older adults. Once an MHR estimate is chosen, the Karvonen method converts it into a target heart rate by factoring in resting heart rate (via Heart Rate Reserve) rather than just applying a flat percentage of MHR, which produces more personalized training zones for people with different fitness levels.
Haskell & Fox (220 − age) is simpler and more widely known, making it fine for casual use. Tanaka (208 − 0.7×age) is generally considered more accurate, particularly for people over 40, since it was derived from a larger and more representative research sample and predicts a slightly higher max heart rate at older ages.
Two people with the same max heart rate can have very different fitness levels, reflected in their resting heart rate — a fitter person typically has a lower resting heart rate. By incorporating Heart Rate Reserve (MHR minus resting HR), the Karvonen method produces a target zone personalized to actual cardiovascular fitness, not just age.
Roughly 50-60% intensity corresponds to light aerobic activity, 60-70% to fat-burning/moderate zones, 70-85% to cardio/endurance training zones, and above 85% to high-intensity anaerobic training — the appropriate zone depends on individual fitness goals.
Plain-language explainers that sit next to this tool.
Picking the wrong domain name can quietly hurt your traffic and branding for years. Follow these seven rules before you register anything.
Calculating working days between two dates means excluding weekends and public holidays from the total. Learn the formula, a worked example, and when this matters most.
Love calculators turn names or birthdates into a compatibility percentage using simple algorithms, not psychology or science. Here is what actually drives the number, and what real compatibility research says instead.
Should you keep renting or buy a home? Compare the true long-term cost of renting versus buying with a worked example, opportunity cost, and the break-even math that actually matters.
Search 190+ free tools by name, or pick a category below. Every one runs instantly in your browser — no signup, nothing to install.
