Target Heart Rate Zone Calculator — Free Online Calculator & Guide

Calculate your 5 training heart rate zones using the Karvonen formula or percentage of max HR. Free, instant, and accurate.

✓ Formula verified: January 2026For informational purposes only

Goal

Heart Rate Zones

Results below

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Estimated Maximum Heart Rate (220 − Age)

185 bpm

Resting Heart Rate

▲ 65 bpm

Heart Rate Reserve (HRR = Max − Resting)

120 bpm

Formula

Karvonen: Target HR = (Max HR − RHR) × Intensity + RHR

Zone 1 — Warm Up / Recovery (50–60% HRR)

125–137 bpm · Light activity, active recovery, promotes blood flow without fatigue

Zone 2 — Fat Burn / Aerobic Base (60–70% HRR)

▲ 137–149 bpm · Optimal fat oxidation, endurance base building, easy conversational pace

Zone 3 — Aerobic / Cardio (70–80% HRR)

▲ 149–161 bpm · Improved cardiovascular efficiency, lactate threshold training

Zone 4 — Anaerobic / Threshold (80–90% HRR)

161–173 bpm · Speed and power development, pushes lactate threshold higher

Zone 5 — VO2 Max / All-Out (90–100% HRR)

▼ 173–185 bpm · Maximum oxygen uptake, speed intervals, short bursts only (30–60 sec)

80/20 Rule — Recommended Training Distribution

▲ 80% in Zone 1–2 (125–149 bpm) | 20% in Zone 4–5

What if your age changes? 31.5 years → 188.5 bpm · 35 years → 185 bpm · 38.5 years → 181.5 bpm

Scenario Comparison

Conservative (5%)

$16,470.09

$6,470.09 interest

Your scenario (7%)

$20,096.61

$10,096.61 interest

Aggressive (10%)

$27,070.41

$17,070.41 interest

High-risk (14%)

$40,224.71

$30,224.71 interest

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Heart Rate Zones Visual

Karvonen Formula

THR = ((HR_max − HR_rest) × %Intensity) + HR_rest

= ((185 − 65) × %Intensity) + 65

= (120 × %Intensity) + 65

Warm Up / Recovery

125–137bpm

Fat Burn / Aerobic Base

137–149bpm

Aerobic / Cardio

149–161bpm

Anaerobic / Threshold

161–173bpm

VO2 Max / All-Out

173–185bpm

Training Zone Guide

Zone 1 — Warm Up / Recovery

125–137 bpm · 50–60% of HRR

Zone 2 — Fat Burn / Aerobic Base

137–149 bpm · 60–70% of HRR

Zone 3 — Aerobic / Cardio

149–161 bpm · 70–80% of HRR

Zone 4 — Anaerobic / Threshold

161–173 bpm · 80–90% of HRR

Zone 5 — VO2 Max / All-Out

173–185 bpm · 90–100% of HRR

80/20 Rule: 80% of training in Zones 1–2, 20% in Zones 4–5

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Heart Rate ZonesEstimated Maximum Heart Rate (220 − Age): 185 bpm