Select the type of calculation you need and provide the required information.
Unit Conversion
Kilograms (kg)
Pounds (lb)
Ounces (oz)
Grams (g)
Kilograms (kg)
Pounds (lb)
Ounces (oz)
Grams (g)
Body Mass Index (BMI) Calculator
Kilograms (kg)
Pounds (lb)
Centimeters (cm)
Meters (m)
Inches (in)
Feet (ft)
Understanding Weight Calculations
Weight is a fundamental measurement in physics and everyday life, representing the force exerted on an object due to gravity. Different contexts require different units and calculations, from simple unit conversions to more complex health-related indices like the Body Mass Index (BMI).
Weight Unit Conversion
Converting between different units of weight is a common task. The most frequent units include:
Kilograms (kg): The base unit of mass in the International System of Units (SI).
Pounds (lb): Commonly used in the United States and other countries. 1 kg is approximately 2.20462 lbs.
Ounces (oz): A smaller unit, with 1 lb equal to 16 oz.
Grams (g): A metric unit, where 1 kg equals 1000 g.
Our calculator allows you to easily convert values between these common weight units using standard conversion factors.
Body Mass Index (BMI) Calculation
The Body Mass Index (BMI) is a measure used to estimate body fat based on an individual's weight and height. It's a widely used screening tool for weight categories that may lead to health problems. The general formula for BMI is:
BMI = weight (kg) / [height (m)]²
For calculations using other units (like pounds and inches), conversions are applied first:
If weight is in pounds (lb) and height in inches (in), the formula becomes: BMI = [weight (lb) / (height (in))²] * 703. The factor 703 accounts for the difference in units.
BMI categories are generally interpreted as follows:
Below 18.5: Underweight
18.5 – 24.9: Normal weight
25.0 – 29.9: Overweight
30.0 and above: Obesity
Important Note: BMI is a general guideline and does not account for muscle mass, bone density, or body composition. It should not be used as a sole diagnostic tool. Consult a healthcare professional for personalized health advice.
Use Cases for Weight Calculators
These calculators are useful for:
International Travel or Shopping: Converting weights when dealing with different unit systems.
Fitness and Health Tracking: Monitoring weight and calculating BMI for health assessments.
Cooking and Recipes: Adjusting ingredient quantities between metric and imperial units.
Shipping and Logistics: Estimating shipping costs based on weight and destination country standards.
// Conversion Factors
var kgToLb = 2.20462;
var kgToOz = 35.274;
var kgToG = 1000;
var lbToKg = 1 / kgToLb;
var ozToKg = 1 / kgToOz;
var gToKg = 1 / kgToG;
var inchesToMeters = 0.0254;
var feetToMeters = 0.3048;
var metersToInches = 1 / inchesToMeters;
var metersToFeet = 1 / feetToMeters;
function convertWeight() {
var value = parseFloat(document.getElementById("valueToConvert").value);
var fromUnit = document.getElementById("fromUnit").value;
var toUnit = document.getElementById("toUnit").value;
var resultElement = document.getElementById("conversionResult");
resultElement.innerHTML = "; // Clear previous result
if (isNaN(value)) {
resultElement.innerHTML = 'Please enter a valid number.';
return;
}
var valueInKg;
// Convert input value to kilograms first
if (fromUnit === "kg") {
valueInKg = value;
} else if (fromUnit === "lb") {
valueInKg = value * lbToKg;
} else if (fromUnit === "oz") {
valueInKg = value * ozToKg;
} else if (fromUnit === "g") {
valueInKg = value * gToKg;
}
var convertedValue;
// Convert kilograms to the target unit
if (toUnit === "kg") {
convertedValue = valueInKg;
} else if (toUnit === "lb") {
convertedValue = valueInKg * kgToLb;
} else if (toUnit === "oz") {
convertedValue = valueInKg * kgToOz;
} else if (toUnit === "g") {
convertedValue = valueInKg * kgToG;
}
resultElement.innerHTML = 'Result: ' + convertedValue.toFixed(4) + ' ' + toUnit;
}
function calculateBmi() {
var weight = parseFloat(document.getElementById("weightForBmi").value);
var weightUnit = document.getElementById("weightUnit").value;
var height = parseFloat(document.getElementById("heightForBmi").value);
var heightUnit = document.getElementById("heightUnit").value;
var resultElement = document.getElementById("bmiResult");
resultElement.innerHTML = "; // Clear previous result
if (isNaN(weight) || isNaN(height) || weight <= 0 || height <= 0) {
resultElement.innerHTML = 'Please enter valid positive numbers for weight and height.';
return;
}
var weightKg;
var heightM;
// Convert weight to kilograms
if (weightUnit === "kg") {
weightKg = weight;
} else if (weightUnit === "lb") {
weightKg = weight * lbToKg;
}
// Convert height to meters
if (heightUnit === "m") {
heightM = height;
} else if (heightUnit === "cm") {
heightM = height / 100; // Convert cm to meters
} else if (heightUnit === "in") {
heightM = height * inchesToMeters;
} else if (heightUnit === "ft") {
heightM = height * feetToMeters;
}
if (heightM <= 0) {
resultElement.innerHTML = 'Height in meters cannot be zero or negative.';
return;
}
// Calculate BMI
var bmi = weightKg / (heightM * heightM);
var bmiCategory;
if (bmi = 18.5 && bmi = 25 && bmi <= 29.9) {
bmiCategory = "Overweight";
} else {
bmiCategory = "Obesity";
}
resultElement.innerHTML = 'Your BMI is: ' + bmi.toFixed(1) + ' (' + bmiCategory + ')';
}