function calculateDecrease() {
var startVal = document.getElementById('initialValue').value;
var endVal = document.getElementById('finalValue').value;
var duration = document.getElementById('timePeriod').value;
var errorDiv = document.getElementById('errorDisplay');
var resultsDiv = document.getElementById('drcResults');
// Reset display
errorDiv.style.display = 'none';
resultsDiv.style.display = 'none';
// Validation
if (startVal === " || endVal === ") {
errorDiv.innerText = "Please enter both Initial and Final values.";
errorDiv.style.display = 'block';
return;
}
var s = parseFloat(startVal);
var e = parseFloat(endVal);
var t = parseFloat(duration);
if (isNaN(s) || isNaN(e)) {
errorDiv.innerText = "Please enter valid numbers.";
errorDiv.style.display = 'block';
return;
}
if (s === 0) {
errorDiv.innerText = "Initial value cannot be zero for rate calculations.";
errorDiv.style.display = 'block';
return;
}
// Logic
var diff = s – e;
var percentDec = (diff / s) * 100;
// Linear Rate
var linearRateStr = "N/A (Enter Time)";
var compoundRateStr = "N/A (Enter Time)";
if (duration !== " && !isNaN(t) && t > 0) {
var linearRate = diff / t;
linearRateStr = linearRate.toFixed(2) + " units / period";
// Compound Decay Rate: End = Start * (1 – r)^t => r = 1 – (End/Start)^(1/t)
// Note: If End is negative, compound rate calculation is complex (imaginary numbers), handle strictly positive logic for decay usually.
if (e >= 0 && s > 0) {
var ratio = e / s;
var compoundRate = (1 – Math.pow(ratio, 1/t)) * 100;
compoundRateStr = compoundRate.toFixed(4) + "% / period";
} else {
compoundRateStr = "N/A (Requires positive values)";
}
}
// Display Results
document.getElementById('resPercentDecrease').innerText = percentDec.toFixed(2) + "%";
document.getElementById('resAbsoluteDiff').innerText = diff.toFixed(2);
document.getElementById('resLinearRate').innerText = linearRateStr;
document.getElementById('resCompoundRate').innerText = compoundRateStr;
resultsDiv.style.display = 'block';
}
Understanding the Decrease Rate Calculator
Whether you are tracking business depreciation, analyzing population decline, or measuring weight loss, calculating the rate of decrease is essential for understanding trends over time. This Decrease Rate Calculator helps you quantify how much a value has dropped, both as a total percentage and as a rate over specific time intervals.
How to Use This Calculator
The tool requires three simple inputs to generate a comprehensive analysis:
Initial Value: The starting point of your data (e.g., revenue last year, initial weight, original asset price).
Final Value: The current or ending point of your data.
Time Duration: The number of periods that have passed between the initial and final values (e.g., 5 years, 30 days). This is optional for simple percentage decrease but required for rate calculations.
The Formulas Behind the Calculation
There are different ways to express a decrease, depending on whether you need a simple percentage or a time-based rate.
1. Total Percentage Decrease
This metric shows the drop relative to the starting value. It is commonly used for discounts or simple comparisons.
This is critical for scenarios where the decrease slows down as the value gets smaller (e.g., radioactive decay, asset depreciation, or customer churn). It calculates the constant percentage lost per period.
If you bought a server for 10,000 (Initial) and it is worth 2,000 (Final) after 5 years (Time):
Total Decrease: 80% of value lost.
Linear Drop: 1,600 per year.
Compound Decay: Approximately 27.52% per year.
Weight Loss Tracking
If an individual goes from 90kg to 85kg over 10 weeks:
Total Loss: 5.56%.
Rate: 0.5kg per week on average.
Why Distinction Matters
Confusing a linear rate with a compound rate can lead to significant errors in forecasting. In finance and science, the Compound Decay Rate is usually the more accurate metric for projecting future values because it accounts for the changing base value over time.