Every length and weight unit here is defined as a fixed multiple of one base unit — meters for length, grams for weight. A foot is defined as exactly 0.3048 meters, so converting 1 meter to feet is just 1 ÷ 0.3048 = 3.28084 ft (the calculator's own default conversion). A kilogram is exactly 453.592 grams per pound, so 1 kg to lb is a single division too. Because every unit in the same category shares one common reference point, converting between any two of them — say, inches directly to yards — is really just converting through that shared base unit as an invisible middle step.
Temperature scales don't share a common zero point the way length and weight units do — 0°C means "water freezes," while 0°F refers to a completely different historical reference. That's why converting temperature needs both a scale factor and an offset: °F = °C × 9⁄5 + 32. A clean way to see it: normal human body temperature, 37°C, converts to exactly 98.6°F — and the two textbook anchor points, water's freezing point (0°C) and boiling point (100°C), land at exactly 32°F and 212°F. No multiplication-only formula could produce both of those correctly at once, which is exactly why temperature needs its own conversion path instead of a simple factor like every other unit here.
Conversions use standard, internationally recognized conversion factors and are accurate to several decimal places.
Temperature scales don't start at zero in the same place, so converting requires an offset calculation rather than just multiplying by a fixed factor.
Common length units (millimeters to miles), weight units (milligrams to stone), and Celsius, Fahrenheit, and Kelvin for temperature.