The per thousand rate, also known as "per mille" (represented by the symbol ‰), is a numerical value used to describe how many units of a specific item exist within a total group of one thousand. It is mathematically similar to percentages (per hundred), but it offers more precision for small frequencies.
How to Calculate Per Thousand Rate
Calculating a rate per thousand is straightforward. You divide the number of specific events by the total population and then multiply the result by 1,000.
Rate per Thousand (‰) = (Event Count / Total Population) × 1,000
Step-by-Step Calculation Example
Imagine a town has a population of 25,000 people and records 150 births in a single year. To find the birth rate per thousand:
Divide the births by the total population: 150 ÷ 25,000 = 0.006
Multiply by 1,000: 0.006 × 1,000 = 6
Result: The birth rate is 6 per thousand (6‰).
Common Uses of Per Thousand Rates
Demographics: Measuring crude birth rates, death rates, or marriage rates in a country.
Manufacturing: Tracking defect rates in quality control where errors are rare.
Oceanography: Measuring salinity (the salt content of seawater).
Finance: Millage rates are often used in property tax assessments.
function calculateMilleRate() {
var count = document.getElementById("eventCount").value;
var total = document.getElementById("totalPopulation").value;
var resultDiv = document.getElementById("calc-result");
var resultText = document.getElementById("resultText");
var numCount = parseFloat(count);
var numTotal = parseFloat(total);
if (isNaN(numCount) || isNaN(numTotal)) {
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#fce4e4";
resultDiv.style.borderLeftColor = "#e74c3c";
resultText.innerHTML = "Error: Please enter valid numbers in both fields.";
return;
}
if (numTotal === 0) {
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#fce4e4";
resultDiv.style.borderLeftColor = "#e74c3c";
resultText.innerHTML = "Error: Total population cannot be zero.";
return;
}
var rate = (numCount / numTotal) * 1000;
resultDiv.style.display = "block";
resultDiv.style.backgroundColor = "#e8f6ef";
resultDiv.style.borderLeftColor = "#27ae60";
resultText.innerHTML = "The rate is " + rate.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 4}) + " ‰ (per thousand).";
}