How to use the tool

• Beats counted – Type the beats you felt. Examples: 32 or 45.
• Time interval (s) – Enter the seconds you timed. Examples: 20 or 30.
• Age (years) – Needed for the 220 – age formula. Examples: 25 or 50.
• Resting heart rate (optional) – Your morning pulse. Examples: 55 or 70 bpm.
• Intensity level – Choose Light, Moderate, Vigorous, or Maximum.
• Press “Calculate” to view BPM, maximum heart rate, target zone, and heart-rate reserve.

Formulas

Calculated heart rate:

$$HR = rac{\text{Beats}}{\text{Seconds}} \times 60$$

Maximum heart rate:

$$MHR = 220 – \text{Age}$$

Heart-rate reserve:

$$HRR = MHR – RHR$$

Target zone (Karvonen):

$$THR = (HRR \times \text{Intensity}) + RHR$$

Example 1 – Moderate effort

• 32 beats in 20 s → $$HR = rac{32}{20}\times60 = 96\;bpm$$
• Age 25 → $$MHR = 195\;bpm$$
• Zone 60–70 % → 117–137 bpm
• With RHR 55 bpm → $$HRR = 140$$; Karvonen zone 139–153 bpm

Example 2 – Vigorous effort

• 45 beats in 30 s → $$HR = rac{45}{30}\times60 = 90\;bpm$$
• Age 50 → $$MHR = 170\;bpm$$
• Zone 70–85 % → 119–145 bpm
• With RHR 70 bpm → $$HRR = 100$$; Karvonen zone 140–155 bpm

Quick-Facts

• 220 – age rule estimates peak heart rate within ±12 bpm (Robergs & Landwehr, 2002).
• Resting heart rate for healthy adults is 60–100 bpm (AHA, 2023).
• ACSM calls 64–76 % MHR “moderate” intensity (ACSM Guidelines, 2021).
• Endurance gains appear after 150 min/week of moderate exercise (CDC, 2023).

FAQ

What is beats-per-minute?

BPM is the number of heart contractions in one minute; resting adults average 60–100 bpm (AHA, 2023).

How do I measure resting heart rate accurately?

Check your pulse in bed after waking, count 30 s, double the result, repeat three mornings, and average (AHA, 2023).

Why does the tool use 220 – age?

The equation predicts maximal heart rate for large adult samples with ±10 % error (Tanaka et al., 2001).

What are heart rate zones?

Zones slice MHR into intensity bands—light (50–60 %), moderate (60–70 %), vigorous (70–85 %), maximum (85–95 %)—guiding training load (ACSM, 2021).

How does heart-rate reserve improve targeting?

HRR tailors zones by subtracting resting rate, then adding it back after scaling, personalising effort (Karvonen & Vuorimaa, 1988).

Which zone burns the most fat?

Fat oxidation peaks near 65 % MHR; however, total calorie burn rises with intensity (Achten & Jeukendrup, 2004).

When should I stop exercising based on heart rate?

Stop if HR exceeds 95 % MHR or symptoms appear; over-reaching raises cardiac risk (Thompson et al., Circulation 2020).

How often should I check heart rate during workouts?

Every 5–10 minutes or when intensity changes keeps you within your planned zone (ACSM, 2021).