6 – No exertion at all
7 – Extremely light
8 – Very light
9 – Very light
10 – Light
11 – Light
12 – Somewhat hard
13 – Somewhat hard
14 – Hard (Heavy)
15 – Hard (Heavy)
16 – Very hard
17 – Very hard
18 – Extremely hard
19 – Extremely hard
20 – Maximal exertion
Calculation Results:
Borg Standard Estimate: — BPM
Karvonen Adjusted HR: — BPM
Intensity Level: —
*Note: Borg Standard is a general estimate (RPE x 10). Adjusted HR uses your age and resting heart rate for better accuracy.
What is RPE?
RPE stands for Rate of Perceived Exertion. It is a scientific way to measure the intensity of your exercise based on how hard you feel your body is working. The most common tool is the Borg Rating of Perceived Exertion Scale, which ranges from 6 to 20.
The Borg Scale (6-20) vs. Heart Rate
Dr. Gunnar Borg developed this scale to correlate directly with heart rate. The logic is simple: if you multiply your RPE score by 10, it should roughly represent your current heart rate in beats per minute (BPM). For example, an RPE of 13 (somewhat hard) suggests a heart rate of approximately 130 BPM.
Why Use an RPE Calculator?
While heart rate monitors are common, they aren't always available or accurate (due to wrist-sensor lag). Learning to gauge your RPE allows you to:
Listen to your body: Adjust intensity based on fatigue, heat, or stress.
Train in specific zones: Ensure you are hitting aerobic or anaerobic thresholds.
Safety: Prevent overexertion during recovery or rehab sessions.
RPE Intensity Chart
RPE Score
Exertion Level
Example Activity
6 – 8
Very Light
Slow walking, tying shoes
9 – 11
Light
Easy jogging, warm-up
12 – 14
Somewhat Hard
Steady-state cardio, brisk cycling
15 – 16
Hard
Heavy lifting, fast running
17 – 19
Very Hard
Sprints, HIIT finish
20
Maximal
Absolute limit, cannot continue
Example Calculation
If a 40-year-old individual with a resting heart rate of 60 BPM is training at an RPE of 15 ("Hard"):
Borg Estimate: 15 x 10 = 150 BPM.
Max HR: 220 – 40 = 180 BPM.
Heart Rate Reserve: 180 – 60 = 120 BPM.
Adjusted Result: Training at 64% intensity (based on scale position) leads to an adjusted HR of roughly 137-150 BPM depending on fitness level.
function calculateRPEHeartRate() {
var age = document.getElementById("userAge").value;
var restingHR = document.getElementById("restingHR").value;
var rpe = document.getElementById("rpeScore").value;
var resultDiv = document.getElementById("rpeResult");
// Validation
if (!age || age 120) {
alert("Please enter a valid age.");
return;
}
if (!restingHR || restingHR 150) {
alert("Please enter a valid resting heart rate (30-150).");
return;
}
// Convert to numbers
age = parseFloat(age);
restingHR = parseFloat(restingHR);
rpe = parseFloat(rpe);
// 1. Borg Standard Estimate
var borgEst = rpe * 10;
// 2. Karvonen Adjusted HR
// The Borg scale 6-20 maps to roughly 0% to 100% intensity.
// Calculation: (RPE – 6) / (20 – 6) = percentage of intensity
var maxHR = 220 – age;
var hrReserve = maxHR – restingHR;
var intensityPerc = (rpe – 6) / 14;
var karvonenEst = (hrReserve * intensityPerc) + restingHR;
// Intensity Level Description
var description = "";
if (rpe <= 8) {
description = "Very Light (Recovery)";
} else if (rpe <= 11) {
description = "Light (Aerobic Base)";
} else if (rpe <= 14) {
description = "Moderate (Tempo)";
} else if (rpe <= 16) {
description = "Hard (Threshold)";
} else if (rpe <= 19) {
description = "Very Hard (Anaerobic)";
} else {
description = "Maximal (VO2 Max)";
}
// Display Results
document.getElementById("borgEst").innerHTML = Math.round(borgEst);
document.getElementById("karvonenEst").innerHTML = Math.round(karvonenEst);
document.getElementById("intensityLevel").innerHTML = description;
resultDiv.style.display = "block";
}