Heart Rate Zones for Triathletes: Calculator + the 5-Zone Guide

Five zones, two numbers, one calculator. Enter your maximum and resting heart rate below and you get your personal training zones instantly — then read on for what each zone is actually for, because owning the numbers matters less than knowing why 80% of your training should sit in the two easiest ones.

Finding your two numbers

• Resting HR: average your watch's sleeping/resting reading over a normal week, or count your pulse before getting out of bed.
• Max HR: forget 220-minus-age — it misses real athletes by up to 15 beats either way. Use the highest value you have seen in a hard race finish, or do a field test: after a long warm-up, run 3 × 3 minutes uphill, each harder than the last, sprinting the final 30 seconds. The peak you record is close enough.
• Heart rate also differs by sport: most athletes see a cycling max about 5–8 beats lower than their running max. Serious cyclists should set separate bike zones — or better, train with power.

What each zone is for

Zone 1 — Recovery (50–60% HRR)

Active recovery, warm-ups, the day after a race. If it feels pointless, it is working.

Zone 2 — Endurance (60–70% HRR)

The engine room. Fat metabolism, capillary growth, mitochondrial density — the adaptations that decide your Ironman. Conversational pace. Most athletes should log the majority of weekly hours here.

Zone 3 — Tempo (70–80% HRR)

"Comfortably hard." Long-course race pace lives at the bottom of this zone — and so does the classic age-grouper trap of training here every day: hard enough to tire you, not hard enough to sharpen you.

Zone 4 — Threshold (80–90% HRR)

Cruise intervals, 10K-to-half-marathon effort, FTP work on the bike. One or two quality sessions a week, not more.

Zone 5 — VO2 Max (90–100% HRR)

Three-to-five-minute intervals that raise your ceiling. Potent, expensive, used sparingly — our VO2 max strategy guide shows the Zone 2 + HIIT split.

The 80/20 rule

Decades of elite training data converge on the same split: roughly 80% of sessions easy (Z1–Z2), 20% genuinely hard (Z4–Z5), and surprisingly little in between. Age groupers usually do the opposite — everything medium — and plateau. If your easy days feel embarrassingly slow and your hard days scare you a little, your distribution is right.

FAQ

Why does my heart rate drift up on a steady easy run?

Cardiac drift — heat, dehydration and fatigue push HR up at constant pace. A few beats is normal; 15+ means the pace was not actually easy, or you need fluids. We cover the mechanism in why your heart rate runs high.

Heart rate, pace or power — which should rule?

On the bike: power first, HR as a health check. Running: pace on the track, HR on hills and long runs. Everywhere: HR is the honest adjudicator on hot or tired days.

My zones feel wrong — Zone 2 feels too easy.

That is the most common sign they are finally right. If genuinely off, your max-HR estimate is probably low; retest with the hill protocol.