Meter (m)
Kilometer (km)
Centimeter (cm)
Millimeter (mm)
Mile (mi)
Yard (yd)
Foot (ft)
Inch (in)
Kilogram (kg)
Gram (g)
Milligram (mg)
Tonne (t)
Pound (lb)
Ounce (oz)
Liter (L)
Milliliter (mL)
Cubic Meter (m³)
US Gallon (gal)
US Quart (qt)
US Cup (cup)
US Fluid Ounce (fl oz)
Celsius (°C)
Fahrenheit (°F)
Kelvin (K)
Meter (m)
Kilometer (km)
Centimeter (cm)
Millimeter (mm)
Mile (mi)
Yard (yd)
Foot (ft)
Inch (in)
Kilogram (kg)
Gram (g)
Milligram (mg)
Tonne (t)
Pound (lb)
Ounce (oz)
Liter (L)
Milliliter (mL)
Cubic Meter (m³)
US Gallon (gal)
US Quart (qt)
US Cup (cup)
US Fluid Ounce (fl oz)
Celsius (°C)
Fahrenheit (°F)
Kelvin (K)
Result: —
Understanding Metric to Metric Unit Conversions
The Metric to Metric Unit Converter is a vital tool for anyone working with measurements across different scales within the metric system, or converting between metric and commonly used imperial units. Accurate unit conversion is fundamental in fields like science, engineering, international trade, cooking, and everyday life. This calculator simplifies the process by handling various units of length, mass, volume, and temperature.
How it Works: The Underlying Math
The core of this calculator relies on established conversion factors. Each unit is typically related to a base unit (e.g., meters for length, kilograms for mass, liters for volume). Conversions involve multiplying or dividing by these factors.
Length Conversions:
The base unit for length in the metric system is the meter (m). All other metric length units are powers of 10 relative to the meter:
1 kilometer (km) = 1000 meters
1 centimeter (cm) = 0.01 meters
1 millimeter (mm) = 0.001 meters
Conversions to/from imperial units (miles, yards, feet, inches) use specific, internationally agreed-upon factors. For example:
1 mile ≈ 1609.34 meters
1 foot = 0.3048 meters
1 inch = 0.0254 meters
Mass Conversions:
The base unit for mass is the kilogram (kg), though the gram (g) is often used as a reference.
1 kilogram (kg) = 1000 grams
1 milligram (mg) = 0.001 grams
1 tonne (t) = 1000 kilograms
Imperial conversions include:
1 pound (lb) ≈ 0.453592 kilograms
1 ounce (oz) ≈ 0.0283495 kilograms
Volume Conversions:
The base metric unit for volume is the liter (L) or cubic meter (m³).
1 cubic meter (m³) = 1000 liters
1 liter (L) = 1000 milliliters (mL)
Imperial conversions include:
1 US gallon ≈ 3.78541 liters
1 US fluid ounce ≈ 0.0295735 liters
Temperature Conversions:
Temperature conversions are non-linear:
Celsius (°C) to Fahrenheit (°F): F = (C * 9/5) + 32
Fahrenheit (°F) to Celsius (°C): C = (F – 32) * 5/9
Celsius (°C) to Kelvin (K): K = C + 273.15
Kelvin (K) to Celsius (°C): C = K – 273.15
Fahrenheit (°F) to Kelvin (K): K = (F – 32) * 5/9 + 273.15
Kelvin (K) to Fahrenheit (°F): F = (K – 273.15) * 9/5 + 32
Use Cases
International Projects: Seamlessly convert measurements between metric and imperial systems used by different partners.
Scientific Research: Ensure consistency in data reporting and experimental setup, especially when collaborating globally.
Cooking and Baking: Convert recipes from metric measurements (grams, liters) to imperial (ounces, cups) or vice versa.
Travel: Understand local distances, temperatures, and fuel measurements.
DIY Projects: Adapt plans or instructions that use different measurement systems.
This calculator provides a reliable and user-friendly way to handle these essential conversions, eliminating the need for complex manual calculations.
function convertUnits() {
var value = parseFloat(document.getElementById("valueToConvert").value);
var fromUnit = document.getElementById("fromUnit").value;
var toUnit = document.getElementById("toUnit").value;
var resultElement = document.getElementById("result").querySelector("span");
if (isNaN(value)) {
resultElement.textContent = "Invalid Input";
return;
}
var convertedValue = value;
var baseUnit = ""; // Base unit for conversion, usually SI base unit or a reference
// — Define Conversion Factors to a common base unit —
// Length Base: Meter (m)
var lengthFactors = {
"meter": 1,
"kilometer": 1000,
"centimeter": 0.01,
"millimeter": 0.001,
"mile": 1609.344,
"yard": 0.9144,
"foot": 0.3048,
"inch": 0.0254
};
// Mass Base: Kilogram (kg)
var massFactors = {
"kilogram": 1,
"gram": 0.001,
"milligram": 0.000001,
"tonne": 1000,
"pound": 0.45359237,
"ounce": 0.0283495231
};
// Volume Base: Liter (L)
var volumeFactors = {
"liter": 1,
"milliliter": 0.001,
"cubicmeter": 1000,
"usgallon": 3.78541,
"usquart": 0.946353,
"uscup": 0.24, // Approximate US legal cup
"usfluidounce": 0.0295735
};
// Temperature requires special handling
if (fromUnit.startsWith("celsius") || toUnit.startsWith("celsius") ||
fromUnit.startsWith("fahrenheit") || toUnit.startsWith("fahrenheit") ||
fromUnit.startsWith("kelvin") || toUnit.startsWith("kelvin")) {
// Handle Temperature Conversions
if (fromUnit === toUnit) {
convertedValue = value;
} else if (fromUnit === "celsius") {
if (toUnit === "fahrenheit") {
convertedValue = (value * 9/5) + 32;
} else if (toUnit === "kelvin") {
convertedValue = value + 273.15;
} else { // celsius to celsius
convertedValue = value;
}
} else if (fromUnit === "fahrenheit") {
if (toUnit === "celsius") {
convertedValue = (value – 32) * 5/9;
} else if (toUnit === "kelvin") {
convertedValue = (value – 32) * 5/9 + 273.15;
} else { // fahrenheit to fahrenheit
convertedValue = value;
}
} else if (fromUnit === "kelvin") {
if (toUnit === "celsius") {
convertedValue = value – 273.15;
} else if (toUnit === "fahrenheit") {
convertedValue = (value – 273.15) * 9/5 + 32;
} else { // kelvin to kelvin
convertedValue = value;
}
} else { // If one of them is temperature but not the other, it's an error or needs specific cross-conversion logic
// This case implies trying to convert e.g. Celsius to Kilogram, which is invalid.
// For simplicity, we'll just show an error if units are mixed inappropriately,
// but the UI should ideally prevent this by grouping or filtering.
// If both are the same temp unit, value remains unchanged, handled above.
if (!fromUnit.includes("temp") || !toUnit.includes("temp")) {
resultElement.textContent = "Invalid Unit Combination";
return;
}
}
resultElement.textContent = convertedValue.toFixed(4); // Use toFixed for temperature precision
return;
}
// — Handle other unit types —
var conversionFactors = {};
if (fromUnit.includes("meter") || fromUnit.includes("kilometer") || fromUnit.includes("centimeter") || fromUnit.includes("millimeter") || fromUnit.includes("mile") || fromUnit.includes("yard") || fromUnit.includes("foot") || fromUnit.includes("inch")) {
conversionFactors = lengthFactors;
baseUnit = "meter"; // All length conversions go through meters
} else if (fromUnit.includes("kilogram") || fromUnit.includes("gram") || fromUnit.includes("milligram") || fromUnit.includes("tonne") || fromUnit.includes("pound") || fromUnit.includes("ounce")) {
conversionFactors = massFactors;
baseUnit = "kilogram"; // All mass conversions go through kilograms
} else if (fromUnit.includes("liter") || fromUnit.includes("milliliter") || fromUnit.includes("cubicmeter") || fromUnit.includes("gallon") || fromUnit.includes("quart") || fromUnit.includes("cup") || fromUnit.includes("fluidounce")) {
conversionFactors = volumeFactors;
baseUnit = "liter"; // All volume conversions go through liters
} else {
resultElement.textContent = "Unsupported Unit Type";
return;
}
// Check if the 'toUnit' belongs to the same category
var toUnitCategory = "";
if (toUnit.includes("meter") || toUnit.includes("kilometer") || toUnit.includes("centimeter") || toUnit.includes("millimeter") || toUnit.includes("mile") || toUnit.includes("yard") || toUnit.includes("foot") || toUnit.includes("inch")) toUnitCategory = "length";
else if (toUnit.includes("kilogram") || toUnit.includes("gram") || toUnit.includes("milligram") || toUnit.includes("tonne") || toUnit.includes("pound") || toUnit.includes("ounce")) toUnitCategory = "mass";
else if (toUnit.includes("liter") || toUnit.includes("milliliter") || toUnit.includes("cubicmeter") || toUnit.includes("gallon") || toUnit.includes("quart") || toUnit.includes("cup") || toUnit.includes("fluidounce")) toUnitCategory = "volume";
var fromUnitCategory = "";
if (fromUnit.includes("meter") || fromUnit.includes("kilometer") || fromUnit.includes("centimeter") || fromUnit.includes("millimeter") || fromUnit.includes("mile") || fromUnit.includes("yard") || fromUnit.includes("foot") || fromUnit.includes("inch")) fromUnitCategory = "length";
else if (fromUnit.includes("kilogram") || fromUnit.includes("gram") || fromUnit.includes("milligram") || fromUnit.includes("tonne") || fromUnit.includes("pound") || fromUnit.includes("ounce")) fromUnitCategory = "mass";
else if (fromUnit.includes("liter") || fromUnit.includes("milliliter") || fromUnit.includes("cubicmeter") || fromUnit.includes("gallon") || fromUnit.includes("quart") || fromUnit.includes("cup") || fromUnit.includes("fluidounce")) fromUnitCategory = "volume";
if (fromUnitCategory !== toUnitCategory) {
resultElement.textContent = "Cannot convert between different types (e.g., Length to Mass)";
return;
}
// — Perform Conversion —
// 1. Convert the input value to the base unit
var valueInBaseUnit = value * conversionFactors[fromUnit];
// 2. Convert from the base unit to the target unit
// Avoid division by zero if conversionFactors[toUnit] is 0, though unlikely with these factors
if (conversionFactors[toUnit] !== undefined && conversionFactors[toUnit] !== 0) {
convertedValue = valueInBaseUnit / conversionFactors[toUnit];
} else {
resultElement.textContent = "Conversion Error";
return;
}
resultElement.textContent = convertedValue.toFixed(4); // Display with 4 decimal places for precision
}
function resetForm() {
document.getElementById("valueToConvert").value = "";
document.getElementById("fromUnit").selectedIndex = 0;
document.getElementById("toUnit").selectedIndex = 0;
document.getElementById("result").querySelector("span").textContent = "—";
}