Units conversion is a fundamental process in science, engineering, and everyday life. It involves changing a measurement from one unit to another, while preserving its actual physical value. For example, converting kilometers to miles, or kilograms to pounds. Accurate conversions are crucial for ensuring consistency, comparability, and correctness in calculations and communications.
This calculator allows you to convert between common units across several categories: Length, Mass, Temperature, and Volume.
How it Works
The calculator uses established conversion factors. For most units, this involves multiplying or dividing the original value by a specific constant. For instance, to convert meters to feet, you multiply by approximately 3.28084.
The general formula for most conversions is:
Converted Value = Original Value × Conversion Factor or
Converted Value = Original Value / Conversion Factor
Temperature conversions are slightly different as they involve both scaling and shifting:
Celsius to Fahrenheit: (°C × 9/5) + 32 = °F
Fahrenheit to Celsius: (°F – 32) × 5/9 = °C
Celsius to Kelvin: °C + 273.15 = K
Kelvin to Celsius: K – 273.15 = °C
Fahrenheit to Kelvin: ( (°F – 32) × 5/9 ) + 273.15 = K
The calculator handles these different formulas based on the selected source and target units.
Common Use Cases
International Travel: Understanding distances (miles vs. kilometers), temperatures, or weights.
Cooking & Baking: Converting between metric (grams, milliliters) and imperial (ounces, cups) measurements.
DIY Projects: Ensuring measurements are correct when using instructions from different regions (e.g., lumber lengths in feet vs. meters).
Scientific Research: Standardizing measurements to a common system (like SI units) for data analysis and collaboration.
Health & Fitness: Tracking weight in kilograms or pounds, or body temperature.
Using a reliable units conversion tool like this calculator ensures accuracy and saves time.
function convertUnits() {
var value = parseFloat(document.getElementById("valueToConvert").value);
var sourceUnit = document.getElementById("sourceUnit").value;
var targetUnit = document.getElementById("targetUnit").value;
var result = "";
if (isNaN(value)) {
document.getElementById("result").innerText = "Please enter a valid number.";
return;
}
if (sourceUnit === targetUnit) {
result = value.toFixed(4) + " " + targetUnit;
document.getElementById("result").innerText = result;
return;
}
var baseValue = 0; // Value in a common base unit for the category
// — Conversion Factors (relative to a base unit within each category) —
// Length: Base unit = Meter (m)
var lengthFactors = {
meter: 1,
kilometer: 1000,
centimeter: 0.01,
millimeter: 0.001,
mile: 1609.34,
yard: 0.9144,
foot: 0.3048,
inch: 0.0254
};
// Mass: Base unit = Kilogram (kg)
var massFactors = {
kilogram: 1,
gram: 0.001,
milligram: 0.000001,
pound: 0.453592,
ounce: 0.0283495
};
// Volume: Base unit = Liter (L)
var volumeFactors = {
liter: 1,
milliliter: 0.001,
gallon: 3.78541, // US Gallon
quart: 0.946353, // US Quart
pint: 0.473176, // US Pint
cup: 0.24, // US Cup (approx, slightly varies)
fluid_ounce: 0.0295735, // US Fluid Ounce
cubic_meter: 1000
};
// — Convert to Base Unit —
if (lengthFactors.hasOwnProperty(sourceUnit)) {
baseValue = value * lengthFactors[sourceUnit];
} else if (massFactors.hasOwnProperty(sourceUnit)) {
baseValue = value * massFactors[sourceUnit];
} else if (volumeFactors.hasOwnProperty(sourceUnit)) {
baseValue = value * volumeFactors[sourceUnit];
} else if (sourceUnit === 'celsius') {
baseValue = value; // Celsius is used directly for calculations
} else if (sourceUnit === 'fahrenheit') {
baseValue = (value – 32) * 5 / 9; // Convert F to C first
} else if (sourceUnit === 'kelvin') {
baseValue = value – 273.15; // Convert K to C first
} else {
document.getElementById("result").innerText = "Unsupported source unit.";
return;
}
// — Convert from Base Unit to Target Unit —
var convertedValue = 0;
if (lengthFactors.hasOwnProperty(targetUnit)) {
convertedValue = baseValue / lengthFactors[targetUnit];
} else if (massFactors.hasOwnProperty(targetUnit)) {
convertedValue = baseValue / massFactors[targetUnit];
} else if (volumeFactors.hasOwnProperty(targetUnit)) {
convertedValue = baseValue / volumeFactors[targetUnit];
} else if (targetUnit === 'celsius') {
convertedValue = baseValue; // Already in C if source was temp
} else if (targetUnit === 'fahrenheit') {
convertedValue = (baseValue * 9 / 5) + 32;
} else if (targetUnit === 'kelvin') {
convertedValue = baseValue + 273.15;
} else {
document.getElementById("result").innerText = "Unsupported target unit.";
return;
}
// Display the result with appropriate precision
var precision = 4;
if (targetUnit === 'milligram' || targetUnit === 'milliliter' || targetUnit === 'centimeter' || targetUnit === 'millimeter' || targetUnit === 'inch' || targetUnit === 'foot' || targetUnit === 'ounce') {
precision = 6;
}
if (targetUnit === 'celsius' || targetUnit === 'fahrenheit' || targetUnit === 'kelvin') {
precision = 2;
}
result = convertedValue.toFixed(precision) + " " + targetUnit;
document.getElementById("result").innerText = result;
}