Convert between metric and imperial units instantly. Perfect for distance, weight, temperature, and volume conversions for everyday use and international travel.
The metric system (SI units) is used by most countries worldwide and in all scientific work. Base units include meter (distance), kilogram (mass), second (time), celsius (temperature). The metric system uses consistent decimal logic making conversions straightforward—moving between units involves multiplying or dividing by powers of 10. The imperial system is primarily used in USA, UK (for some measurements), and a few other countries. Base units include foot/mile (distance), pound (weight), Fahrenheit (temperature). Metric advantages include decimal-based simplicity, international standardization, and universal use in science. Imperial advantages include familiarity in countries using them and some practical unit sizes for everyday purposes. Conversion factors between systems: 1 kilometer equals 0.621371 miles, 1 pound equals 0.453592 kilograms, 1 inch equals 2.54 centimeters. Temperature conversion is non-linear due to different zero points and scales: Celsius equals (Fahrenheit minus 32) times 5/9. Most UK now uses metric officially though some imperial measurements persist socially (pounds for body weight, miles for distances). Travel between metric and imperial countries requires familiarity with both systems. Understanding conversions prevents embarrassing errors and enables smooth international communication.
One kilometer equals 0.621371 miles; one mile equals 1.60934 kilometers. For quick mental estimation: multiply kilometers by 0.62 for miles, multiply miles by 1.61 for kilometers. Common conversions: 5 km approximately equals 3.1 miles, 10 km approximately equals 6.2 miles, marathon 42.195 km approximately equals 26.2 miles. Running and walking distances appear significantly different in different units—10 km is substantial distance while 10 miles is considerably longer. Understanding relative distances helps travel planning and fitness tracking. Road signs, speed limits, and distance markers differ between countries; understanding conversions prevents getting lost or speeding unknowingly.
One kilogram equals 2.20462 pounds; one pound equals 0.453592 kilograms. Quick estimate: multiply kilograms by 2.2 for pounds. Common conversions: 70 kg approximately equals 154 lbs, 80 kg approximately equals 176 lbs. UK often uses stones (14 pounds) and pounds for body weight—70 kg approximately equals 11 stone. Metric proves more precise for medical and scientific work. Understanding conversions matters for travel, health records, and fitness tracking across countries. Cooking and baking increasingly include both metric (grams) and imperial (ounces, pounds) measurements.
Formula: Fahrenheit equals (Celsius times 9/5) plus 32. Formula: Celsius equals (Fahrenheit minus 32) times 5/9. Quick mental estimate: double Celsius and add 30 for rough Fahrenheit conversion (introduces error but useful approximation). Common conversions: 0°C equals 32°F (freezing point), 20°C equals 68°F (comfortable room temperature), 37°C equals 98.6°F (human body temperature), 100°C equals 212°F (boiling water). The Celsius scale spans 0-100 for water freezing to boiling. Fahrenheit scale spans 32-212 for the same range, using different reference points. Most of world uses Celsius; USA uses Fahrenheit. Understanding both matters for international weather reports and temperature settings.
One liter equals 0.264172 US gallons; one US gallon equals 3.78541 liters. One imperial gallon (UK) equals 4.54609 liters. Quick estimate: divide liters by 4 for imperial gallons, multiply by 0.264 for US gallons. Common conversions: 1 liter approximately equals 0.26 US gallons, 4 liters approximately equals 1 US gallon, 10 liters approximately equals 2.64 US gallons. Beverage containers, fuel tanks, and liquid medicine often require conversions between systems.
Beyond metric and imperial, various specialized units exist for specific purposes. Nautical miles measure ocean distances (1 nautical mile equals 1.15 statute miles equals 1.852 km) because they relate to Earth's circumference and latitude measurements enabling navigation. Knots measure maritime and aviation speed (1 knot equals 1 nautical mile per hour). Caliber measures bullet and gun barrel diameters in hundredths of inches. Carat measures gemstone weight (1 carat equals 200 milligrams) while karat measures gold purity (24 karat equals pure gold). Decibels measure sound intensity logarithmically rather than linearly. Acres measure land area primarily in agriculture (1 acre equals 4,047 square meters equals 0.405 hectares). Horsepower measures engine power (1 hp equals 746 watts). Joules and calories both measure energy (1 calorie approximately equals 4.184 joules). These specialized conversions matter within specific fields—sailors must understand knots, gemologists must know carats, mechanics must grasp horsepower. Understanding unit context matters as much as conversion factors. Unit confusion caused famous disasters like the Mars Climate Orbiter failure (metric vs imperial unit mismatch losing $327 million spacecraft). Always verify units in technical and scientific work.
100 kilometers to miles: 100 times 0.621371 equals 62.14 miles. Useful for understanding road distances in metric countries. 150 pounds to kilograms: 150 divided by 2.20462 equals 68.04 kilograms. Important for medical appointments abroad. 25°C to Fahrenheit: (25 times 9/5) plus 32 equals 77°F. Nice room temperature. 2 liters to gallons: 2 times 0.264 equals 0.528 US gallons. Common beverage size conversion.