Complete Guide to Unit Conversion
Whether you are cooking with an American recipe, planning a trip abroad, shipping packages, or working on a science project, accurate unit conversion is essential. Our free unit converter supports the most common measurements used in the United States (US customary / imperial system) and the metric system used by most of the world.
Length Conversion: US Customary to Metric
The United States is one of the few countries that still primarily uses the customary system for everyday measurements of length. The basic units are the inch, foot, yard, and mile. The rest of the world uses the metric system based on the meter.
Key conversion factors:
- 1 inch = 25.4 millimeters (exact)
- 1 foot = 0.3048 meters (exact)
- 1 yard = 0.9144 meters
- 1 mile = 1.609344 kilometers
When converting floor plans, furniture dimensions, or running distances, always double-check whether the source uses US or international units. Our length converter makes it simple to switch between inches, feet, yards, miles, millimeters, centimeters, meters, and kilometers in real time.
Weight & Mass: Pounds, Ounces, Kilograms and More
In the United States, body weight, food packages, and shipping weights are usually expressed in pounds (lb) and ounces (oz). Most other countries use kilograms (kg) and grams (g). Note that the US “ton” (short ton) equals 2,000 pounds, while a metric tonne is 1,000 kilograms (approximately 2,204.6 pounds).
Useful conversions:
- 1 pound = 0.45359237 kilograms (exact by international agreement)
- 1 ounce = 28.3495 grams
- 1 stone (UK) = 14 pounds ≈ 6.35 kg
- 1 US ton = 907.185 kg
Our weight converter handles ounces, pounds, stone, US tons, milligrams, grams, kilograms, and metric tons so you can convert recipes, luggage limits, or shipping labels without a calculator.
Temperature: Fahrenheit, Celsius and Kelvin
The United States is almost alone in using the Fahrenheit scale for weather and cooking. The rest of the world (and the scientific community) uses Celsius. Kelvin is the absolute temperature scale used in physics and chemistry.
Formulas:
- °C = (°F − 32) × 5/9
- °F = (°C × 9/5) + 32
- K = °C + 273.15
Common reference points: water freezes at 32°F / 0°C / 273.15 K and boils at 212°F / 100°C / 373.15 K (at standard atmospheric pressure). Use our temperature converter for weather forecasts, oven settings, or lab work.
Currency Converter with Live Exchange Rates
Traveling, shopping online internationally, or sending money abroad requires up-to-date exchange rates. Our currency converter supports more than 30 major world currencies including the US Dollar (USD), Euro (EUR), British Pound (GBP), Japanese Yen (JPY), Chinese Yuan (CNY), Canadian Dollar (CAD), Australian Dollar (AUD), Indian Rupee (INR), Mexican Peso (MXN), and many more.
Exchange rates are sourced from publicly available data and updated regularly. Remember that banks, credit cards, and money-transfer services usually apply a margin or fee on top of the mid-market rate shown here. Always check the final rate offered by your provider before making a transaction.
Why Use an Online Unit Converter?
Manual calculation is prone to error, especially when dealing with fractions or multiple conversion steps. A reliable online unit converter eliminates mistakes, works on any device, and provides instant results. Our tool is designed with a clean, light interface and large touch-friendly controls so it works equally well on smartphones, tablets, and desktops.
Students, teachers, travelers, cooks, engineers, online shoppers, and DIY enthusiasts all benefit from quick access to accurate conversions between the US customary system and the international metric system.
Tips for Accurate Conversions
- Always confirm whether a recipe or blueprint uses US or imperial units versus metric.
- For scientific work, prefer SI (metric) units and absolute temperature (Kelvin) when required.
- When converting currency for travel, factor in bank fees and the difference between cash, card, and ATM rates.
- Keep a small set of common conversion factors memorized (e.g., 1 inch ≈ 2.54 cm, 1 lb ≈ 0.45 kg, 0°C = 32°F).