You pick a category (length, weight, temperature, volume, speed, or area), enter a value, and select the starting unit. For non-temperature categories, the tool multiplies by a factor to convert to a base SI unit, then divides by each target unit's factor. Temperature conversions route through Celsius as an intermediate step. All factors are standard SI conversion constants.
The underlying conversion factors are exact SI definitions (for example, 1 inch = exactly 0.0254 meters). Results are displayed rounded to four decimal places for readability, but the internal math uses the full-precision factor.
Length, weight, and other units scale linearly from a common zero point, so a simple multiply-and-divide works. Temperature scales have different zero points (0°C ≠ 0°F ≠ 0 K), so conversion requires addition/subtraction, not just scaling.
For length and weight, they're essentially the same (1 pound = 1 pound). For volume, they differ slightly — a US gallon is about 3.785 liters while an imperial gallon is about 4.546 liters. This tool uses US customary values.
Not directly — mass-to-volume requires knowing the substance's density. This tool converts within a single category at a time. For specific needs like cooking (grams of flour to cups), try the Cooking Converter.
Estimate only. Results reflect your inputs and standard formulas. Double-check important decisions independently.