function calculateHeartRate() {
// Get input values
var beats = document.getElementById('beatsInput').value;
var duration = document.getElementById('timeInput').value;
// Output elements
var displayBPM = document.getElementById('resBPM');
var displayHz = document.getElementById('resHz');
var displayPeriod = document.getElementById('resPeriod');
var displayHour = document.getElementById('resHour');
var resultsArea = document.getElementById('resultsDisplay');
// Validation
if (beats === "" || duration === "" || duration <= 0 || beats <= 0) {
alert("Please enter valid positive numbers for both beats and duration.");
return;
}
// Convert strings to numbers
var beatsNum = parseFloat(beats);
var durationNum = parseFloat(duration);
// Core Calculations
// 1. Calculate Beats Per Second (Hz)
var beatsPerSecond = beatsNum / durationNum;
// 2. Calculate Beats Per Minute (BPM)
// If the duration is already 60, BPM is beatsNum.
// Logic: (Beats / Duration) * 60
var bpm = beatsPerSecond * 60;
// 3. Calculate Period (Time per single beat)
// Logic: 1 / BeatsPerSecond
var secondsPerBeat = 1 / beatsPerSecond;
// 4. Calculate Beats per Hour
var beatsPerHour = bpm * 60;
// Update Display
displayBPM.innerHTML = Math.round(bpm) + " BPM";
displayHz.innerHTML = beatsPerSecond.toFixed(2) + " beats/sec";
displayPeriod.innerHTML = secondsPerBeat.toFixed(3) + " sec";
displayHour.innerHTML = beatsPerHour.toLocaleString();
// Show results
resultsArea.style.display = "block";
}
How to Calculate Heart Rate per Second
Understanding your heart rate is a fundamental aspect of monitoring cardiovascular health and fitness intensity. While most people are familiar with "Beats Per Minute" (BPM), converting this to Heart Rate per Second (frequency) or the duration of a single cardiac cycle can provide deeper insights into your heart's rhythm and performance.
The Mathematical Formula
To calculate heart rate statistics, we look at the relationship between the number of heartbeats and time. The core formulas used in the calculator above are:
1. Beats Per Second (Frequency): Hz = Total Beats / Total Seconds
2. Beats Per Minute (BPM): BPM = (Total Beats / Total Seconds) × 60
3. Time Per Beat (Period): Period = 1 / Beats Per Second
Step-by-Step Calculation Example
Let's say you want to determine your heart rate metrics but you only want to measure your pulse for a short period, such as 15 seconds.
Measure: You check your pulse and count 18 beats in 15 seconds.
Calculate per Second: Divide 18 by 15. 18 / 15 = 1.2 beats per second.
Calculate BPM: Multiply the beats per second by 60. 1.2 × 60 = 72 BPM.
Calculate Period: Divide 1 by the beats per second. 1 / 1.2 = 0.83 seconds per beat.
This means your heart is contracting once every 0.83 seconds, which is a standard resting rate for a healthy adult.
Why Measure Heart Rate per Second?
While BPM is the clinical standard, understanding beats per second is useful in various scientific and physiological contexts:
ECG Interpretation: On an electrocardiogram (ECG), time is measured in small boxes (seconds/milliseconds). Knowing the seconds per beat helps in measuring intervals like the R-R interval.
High-Intensity Training: In sports science, understanding the rapid frequency of heart beats during max effort (which can exceed 3 beats per second!) puts the mechanical load of the heart into perspective.
Rhythm Regularity: By focusing on the exact time per beat (e.g., 0.8s vs 0.6s), you can better detect Heart Rate Variability (HRV), a key indicator of recovery and stress.
How to Measure Your Pulse
To use this calculator effectively, you need an accurate count of your heartbeats.
Radial Artery: Place your index and middle fingers on the inside of your wrist, below the thumb base.
Carotid Artery: Place your fingers on your neck, just to the side of your windpipe.
Count: Using a stopwatch, count the beats you feel for a set duration (10, 15, or 30 seconds are easiest).
Input: Enter the number of beats and the seconds measured into the calculator above.
Normal Resting Heart Rates
For adults, a normal resting heart rate usually ranges from 60 to 100 BPM (1.0 to 1.66 beats per second). Athletes often have lower resting rates, sometimes below 60 BPM (less than 1 beat per second), indicating efficient heart function.