A walkthrough, end to end.
- 1
Enter your age. The Tanaka formula (208 − 0.7·age) is more accurate than the classic 220 − age.
- 2
Optionally enter your resting heart rate to enable the Karvonen reserve method (more individualized).
- 3
Read your 5 zones with bpm ranges. Most steady-state cardio sits in Z2; intervals push into Z4–Z5.
Tanaka & Karvonen
Max HR = 208 − 0.7 × age (Tanaka, 2001). Zones are percentages of max HR (or HR reserve when resting HR is supplied: target = ((maxHR − rest) × pct) + rest).
What you can do with this.
Fat-burn vs. cardio zones
Z2 (60–70%) burns the highest fat percentage but Z3+ burns more total calories. The 'fat-burn zone' label is misleading — train across all zones for results.
Building aerobic base in Z2
Most endurance plans (80/20 polarized) prescribe ~80% of training time in Z2. It's slower than feels productive but builds the mitochondrial density that supports faster racing later.
VO₂ max intervals
4×4-min intervals at Z5 with 3-min recoveries (Norwegian protocol) is one of the best-studied VO₂-improving sessions. The calculator gives you the bpm range to target.
Tempo and threshold training
Z3–Z4 (70–90% max) is sustainable for 20–60 minutes. Tempo runs improve lactate clearance — one of the highest-yield sessions per training hour for distance runners and cyclists.
Recovery runs in Z1
Z1 (<60% max) is barely above walking heart rate. Use it the day after hard sessions to keep blood flow up without adding fatigue. If your HR drifts above Z1, slow down or walk.
Cycling vs. running zones
Cycling max HR is typically 5–10 bpm lower than running max for the same person — fewer muscles work, less heart demand. If you train both, set zones independently from each sport's max.
Heart rate while pregnant
ACOG removed the old 140-bpm cap in 2002 and now recommends RPE-based monitoring. If you can talk in full sentences, intensity is fine. Always coordinate with your OB if symptoms appear.
Resting heart rate as a fitness marker
Trained adults often sit at 50–60 bpm; elite endurance athletes go below 40. Track resting HR weekly — a sustained 5+ bpm rise often precedes illness or signals overtraining.
Heart rate calculator 2026 — what's current
Wearables now estimate VO₂ max from HR + pace and give individualized lactate thresholds, but the Tanaka/Karvonen math is still what they're built on. Use the calculator as the math reference; let the watch handle live tracking.
Frequently asked.
Tanaka. The classic formula overestimates max HR for adults under 40 and underestimates it for older adults — its standard error is ±10 bpm vs. Tanaka's ±7.
It uses heart rate reserve (max − rest) instead of just max. More individualized, especially for very fit (low resting HR) people.
Heart rate is a poor proxy for resistance-training intensity — RPE and load matter more. Zones are most useful for steady-state and interval cardio.
Caffeine, dehydration, poor sleep, heat, or onset illness can push HR up 10–20 bpm at the same effort. If it persists more than a few days, take an easy week or rest.
Yes — the formula is a population average with ±7 bpm error. A treadmill VO₂ max test or a hard 20-minute time trial gives a more accurate personal max.
No. Calculations run entirely in your browser. There's no server processing, no analytics on inputs, no cookies storing your numbers.