Unit Converter

Metric, Imperial & More

Common Conversions

All Conversions

Conversion Tips

Metric vs Imperial

Only the US, Liberia, and Myanmar use the imperial system. The metric system is used by 95% of the world's population and is the standard in science.

Temperature Trick

Quick Celsius to Fahrenheit: double it and add 30. Quick F to C: subtract 30 and halve. Not exact, but close enough for everyday temperatures.

Unit Prefixes

kilo=1000, mega=10^6, giga=10^9, tera=10^12. For small: milli=10^-3, micro=10^-6, nano=10^-9, pico=10^-12. Each step is 1000x.

Powerful Features

Multiple Categories

Length, weight, temperature, speed, area, volume, and data storage — all in one tool.

Instant Swap

Swap source and target units with a single click for quick reverse conversions.

All Conversions

See your value converted to every unit in the category simultaneously.

Quick Reference

Common conversion reference table helps with everyday conversions.

Full Articles

History

The Metric System: A Brief History of the World's Measurement Standard

The metric system is the most widely used measurement system in the world. Understanding its history helps appreciate why it's the standard in science and most countries.

Origins: Developed in France during the 1790s, the metric system was based on natural constants — the meter was defined as one ten-millionth of the distance from the equator to the North Pole.

Adoption: Today, only three countries (USA, Liberia, Myanmar) don't officially use the metric system. Even in the US, science, medicine, and many industries use metric exclusively.

SI Units: The International System of Units (SI) is the modern form of the metric system, with seven base units: meter, kilogram, second, ampere, kelvin, mole, and candela.

Conversion

Mastering Temperature Conversions: Celsius, Fahrenheit, and Kelvin

Temperature scales are the most common unit conversions people need. Learn the history, formulas, and practical tips for each scale.

Celsius (1742): Based on water's freezing (0°C) and boiling (100°C) points. Used by most countries and in science worldwide.

Fahrenheit (1724): 32°F is water's freezing point, 212°F is boiling. The scale was based on a brine solution's freezing point (0°F) and body temperature (96°F).

Kelvin (1848): The SI unit of temperature. 0K is absolute zero — the coldest possible temperature. Water freezes at 273.15K, boils at 373.15K.

Science

Scientific Notation and Unit Prefixes: From Quetta to Quecto

Scientific notation and SI prefixes allow us to express both the very large and very small in understandable terms. Understanding them is essential for science and engineering.

Large Prefixes: Quetta (10^30), Ronna (10^27), Yotta (10^24), Zetta (10^21), Exa (10^18), Peta (10^15), Tera (10^12), Giga (10^9), Mega (10^6), Kilo (10^3).

Small Prefixes: Milli (10^-3), Micro (10^-6), Nano (10^-9), Pico (10^-12), Femto (10^-15), Atto (10^-18), Zepto (10^-21), Yocto (10^-24).

New Prefixes: In 2022, four new prefixes were added: Ronna, Quetta, Ronto, and Quecto — the first additions in over 30 years.

Practical

Everyday Conversions: Cooking, Driving, and Shopping

Unit conversions aren't just for scientists. We use them every day — from cooking recipes to fuel efficiency to shopping. Here are the most useful everyday conversions.

Cooking Conversions: 1 cup = 240ml, 1 teaspoon = 5ml, 1 tablespoon = 15ml. 1 oz = 28.35g, 1 lb = 453.6g. 1 gallon = 3.785 liters.

Driving Conversions: 1 mile = 1.609 km. Fuel efficiency: 1 mpg ≈ 0.425 km/L. 1 gallon ≈ 3.785 liters. 1 psi ≈ 6.895 kPa.

Shopping Conversions: 1 inch = 2.54 cm. 1 foot = 30.48 cm. 1 yard = 0.9144 m. 1 acre = 4,046.86 m². Understanding these helps when shopping internationally.

Technology

Data Storage Units: From Bits to Yottabytes

Data storage units can be confusing. Understanding bits, bytes, and their multiples is essential in our data-driven world.

Base Units: A bit is the smallest unit (0 or 1). A byte = 8 bits. Everything else is multiples of these. 1 kilobyte = 1024 bytes (2^10).

Common Units: MB (megabytes, 1,048,576 bytes), GB (gigabytes, 1,073,741,824 bytes), TB (terabytes, 1,099,511,627,776 bytes).

Decimal vs. Binary: Hard drive manufacturers use decimal (1GB = 1,000,000,000 bytes) while operating systems use binary (1GB = 1,073,741,824 bytes). This is why your 1TB drive shows as 931GB.

Engineering

Unit Conversion in Engineering: Why Precision Matters

In engineering, unit conversion errors can have catastrophic consequences. Learn why precision in conversion is critical for safety and success.

Famous Disasters: The Mars Climate Orbiter was lost in 1999 because Lockheed Martin used imperial units while NASA used metric units — a $125 million lesson.

Dimensional Analysis: Engineers use dimensional analysis to check calculations. Units must cancel out correctly — if they don't, something's wrong.

Precision Requirements: Aerospace and medical devices require extreme precision. A 1% conversion error in a medical dosage calculation could be fatal.

Navigation

Speed Units: Understanding MPH, KPH, and Knots

Different contexts require different speed units. Understanding when and why each is used helps in navigation and travel.

MPH (Miles Per Hour): Used in the US and UK for road speeds. 1 MPH = 0.447 m/s = 1.609 KPH. The US is one of the few countries still using MPH.

KPH (Kilometers Per Hour): Used in most countries for road speeds. 1 KPH = 0.278 m/s = 0.621 MPH. The standard speed unit in the metric system.

Knots: Used in aviation and maritime navigation. 1 knot = 1 nautical mile per hour = 1.852 KPH = 1.151 MPH. Based on the circumference of the Earth, it's ideal for navigation.

Finance

Currency Conversion: Understanding Exchange Rates

Currency conversion is one of the most important unit conversions in the modern world. Learn about exchange rates, spreads, and what affects currency values.

Exchange Rates: The value of one currency in terms of another. Rates fluctuate based on economic factors, political stability, and market sentiment.

Buying vs. Selling Rates: Banks and exchanges don't use the mid-market rate — they use bid/ask spreads to make a profit. The spread is the difference between buying and selling prices.

Real-Time Rates: For accurate conversions, use real-time sources. Historical rates are useful for tracking long-term trends and planning international transactions.

Unit Converter: A Comprehensive Guide

Unit conversion is an essential skill in various fields, including science, engineering, cooking, and everyday life. This article provides an in-depth look at unit conversion for length, weight, temperature, speed, and area, along with practical examples to enhance understanding.

Length Conversion

Length is a fundamental measurement used to quantify distance. Different systems of measurement exist, with the metric system (meters, centimeters, kilometers) and the imperial system (inches, feet, yards, miles) being the most common.

Common Length Units

Conversion Factors

To convert between metric and imperial units, the following factors are commonly used:

Example Conversions

  1. Converting centimeters to inches:

    If you have 50 cm, the conversion to inches is:

    50 cm × (1 in / 2.54 cm) ≈ 19.69 in

  2. Converting miles to kilometers:

    For 5 miles:

    5 mi × 1.60934 km/mi ≈ 8.05 km

Weight Conversion

Weight measures the force exerted by gravity on an object. Like length, weight can be expressed in different units, including grams, kilograms, pounds, and ounces.

Common Weight Units

Conversion Factors

Conversion between metric and imperial weight units involves the following factors:

Example Conversions

  1. Converting kilograms to pounds:

    For 10 kg:

    10 kg × (2.20462 lb / 1 kg) ≈ 22.05 lb

  2. Converting ounces to grams:

    For 8 oz:

    8 oz × 28.3495 g/oz ≈ 226.8 g

Temperature Conversion

Temperature is a measure of thermal energy. The most common temperature scales are Celsius, Fahrenheit, and Kelvin.

Common Temperature Units

Conversion Formulas

The following formulas can convert between these temperature scales:

  1. Celsius to Fahrenheit:

    F = (C × 9/5) + 32

  2. Fahrenheit to Celsius:

    C = (F − 32) × 5/9

  3. Celsius to Kelvin:

    K = C + 273.15

  4. Kelvin to Celsius:

    C = K − 273.15

Example Conversions

  1. Converting Celsius to Fahrenheit:

    For 25 °C:

    F = (25 × 9/5) + 32 = 77 °F

  2. Converting Fahrenheit to Celsius:

    For 68 °F:

    C = (68 − 32) × 5/9 ≈ 20 °C

Speed Conversion

Speed measures how quickly an object moves. Common units include kilometers per hour (km/h), miles per hour (mph), and meters per second (m/s).

Common Speed Units

Conversion Factors

To convert between these units, use the following factors:

Example Conversions

  1. Converting km/h to mph:

    For 100 km/h:

    100 km/h × 0.621371 mph/km/h ≈ 62.14 mph

  2. Converting mph to m/s:

    For 60 mph:

    60 mph × (0.44704 m/s / 1 mph) ≈ 26.82 m/s

Area Conversion

Area measures the size of a surface. Common units include square meters (m²), square kilometers (km²), acres, and square feet (ft²).

Common Area Units

Conversion Factors

Key conversion factors for area include:

Example Conversions

  1. Converting hectares to acres:

    For 5 hectares:

    5 ha × 2.47105 acres/ha ≈ 12.36 acres

  2. Converting square meters to square feet:

    For 100 m²:

    100 m² × 10.7639 ft²/m² ≈ 1076.39 ft²

Conclusion

Understanding unit conversion is vital for effective communication and comprehension across various domains. By mastering the conversion of length, weight, temperature, speed, and area, individuals can navigate practical applications in daily life, education, and professional settings with confidence. Whether you are cooking, traveling, or conducting scientific research, knowing how to convert units accurately can enhance your skills and knowledge.