<form id="bmr-calculator-form">
<label for="unit-system">Unit system:</label>
<select id="unit-system">
<option value="metric">Metric</option>
<option value="english">English</option>
</select><br><br>
<label for="age">Age:</label>
<input type="number" id="age" required><br><br>
<label for="gender">Gender:</label>
<select id="gender">
<option value="male">Male</option>
<option value="female">Female</option>
</select><br><br>
<label for="weight">Weight:</label>
<input type="number" id="weight" required><span id="weight-unit"> kg</span><br><br>
<label for="height">Height:</label>
<input type="number" id="height" required><span id="height-unit"> cm</span><br><br>
<button type="button" onclick="calculateBMR()">Calculate BMR</button>
</form>
<div id="bmr-result"></div>
<script>
function calculateBMR() {
const unitSystem = document.getElementById("unit-system").value;
const age = parseFloat(document.getElementById("age").value);
const gender = document.getElementById("gender").value;
let weight = parseFloat(document.getElementById("weight").value);
let height = parseFloat(document.getElementById("height").value);
if (unitSystem === "english") {
weight = weight * 0.453592; // Convert pounds to kilograms
height = height * 2.54; // Convert inches to centimeters
}
let bmr;
if (gender === "male") {
bmr = 88.362 + (13.397 * weight) + (4.799 * height) - (5.677 * age);
} else {
bmr = 447.593 + (9.247 * weight) + (3.098 * height) - (4.330 * age);
}
document.getElementById("bmr-result").innerHTML = "Your BMR is: " + bmr.toFixed(2) + " calories/day";
}
document.getElementById("unit-system").addEventListener("change", function() {
const unitSystem = this.value;
const weightUnit = document.getElementById("weight-unit");
const heightUnit = document.getElementById("height-unit");
if (unitSystem === "metric") {
weightUnit.innerHTML = " kg";
heightUnit.innerHTML = " cm";
} else {
weightUnit.innerHTML = " lbs";
heightUnit.innerHTML = " in";
}
});
</script>