Unit Converter
Convert between length, weight, and temperature units.
Your Details
How It Works
- Choose a category — length, weight, or temperature.
- Enter a value and choose the units to convert from and to.
- Press Calculate to see the result in every unit in that category.
Formula Used
Length and weight convert through meters/kilograms; temperature uses direct formulas.
Good to Know
- • Temperature conversion isn't a simple multiplication — it needs an offset too.
- • The full table shows the same value across every unit at once.
Important Notes
- • Covers length, weight, and temperature only in this version.
Why Temperature Conversion Is Different
Length and weight conversions are simple multiplication — there's a single fixed ratio between any two units, so converting is just multiplying by that constant. Temperature is fundamentally different because Celsius, Fahrenheit, and Kelvin don't share a common zero point: 0°C is not 0°F (it's 32°F), and 0°F is not 0°C (it's about -17.8°C). Because the scales are offset from each other rather than simply scaled, temperature conversion needs both a multiplication step and an addition/subtraction step, not a single conversion factor.
Kelvin is the exception that behaves more like length and weight — it shares the same "step size" as Celsius (a 1-degree change means the same thing in both), but its zero point is set at absolute zero rather than the freezing point of water, so converting between Celsius and Kelvin only requires a simple offset, not a scaling factor.
Converting Through a Base Unit
This calculator converts length and weight by first converting the input to a base unit (meters for length, kilograms for weight), then converting from that base unit to the target unit — rather than storing a direct conversion factor between every possible pair of units. This is the same approach most unit conversion systems use internally, since it only requires knowing each unit's relationship to one shared base unit, not to every other unit individually.
The practical benefit is that adding a new unit to the system only requires defining its relationship to the base unit once, and it automatically becomes convertible to every other unit already in the system — a small design choice that makes unit converters far simpler to build and maintain than a giant table of every possible pairwise conversion.
Defining the Basics
- Base unit — the standard reference unit (meters for length, kilograms for weight) used as an intermediate step in conversions.
- Conversion factor — the fixed ratio between two units of the same type, used to multiply or divide during conversion.
- SI units — the International System of Units, the modern metric standard (meters, kilograms, etc.) most conversion factors are built around.
An Example to Follow: Multi-Step Length and Temperature Conversions
Converting 10 kilometers to miles:
10,000 m → miles: 10,000 ÷ 1,609.34 ≈ 6.21 miles
Converting 100°F to Celsius:
°C = (100 − 32) × 5/9 = 68 × 5/9 ≈ 37.8°C
Common Conversion Reference Table
| Conversion | Factor |
|---|---|
| 1 mile | 1.60934 km |
| 1 kilogram | 2.20462 lb |
| 1 inch | 2.54 cm |
| 0°C | 32°F / 273.15K |
What Often Goes Wrong With Unit Conversion
- Applying a multiplication-only approach to temperature — temperature conversion needs an offset in addition to (or instead of) a scaling factor.
- Rounding too early in multi-step conversions — can introduce small but compounding errors, especially when converting through an intermediate base unit.
- Mixing unit systems within one calculation — always confirm whether a figure is in metric or imperial before converting, since the two systems aren't interchangeable without conversion.