Measurement & Conversion Reference Guides

1. Geographic Coordinates: DMS ↔ DDM ↔ Decimal Degrees (DD)

Geographic latitude and longitude are expressed in three main formats: DMS (Degrees, Minutes, Seconds, e.g. 50° 05′ 12.6″ N), DDM (Degrees, Decimal Minutes, e.g. 50° 5.21′ N), and DD (Decimal Degrees, e.g. 50.086833°).

Formula: DD = sign × (Degrees + Minutes / 60 + Seconds / 3600). EveryUnit accepts symbols, space-separated numbers (50 05 12.6), and compact notation without spaces (500512.6).

2. Astronomical Distances: Light Year, Astronomical Unit & Parsec

By definition of the International Astronomical Union (IAU), 1 Julian year is exactly 365.25 days (31,557,600 seconds) and the speed of light in vacuum is exactly 299,792,458 m/s. Therefore 1 light year (ly) equals exactly 9,460,730,472,580.8 kilometers (≈ 5,878,625,373,183.6 miles or 3.103914197×10¹⁶ feet).

One Astronomical Unit (au) is defined as exactly 149,597,870.7 km, and one parsec (pc) is 648,000 / π au (≈ 3.26156 light years).

3. International System of Units (SI) & Exact Definitions

Since the 1959 International Yard and Pound Agreement and the 2019 SI redefinition, customary and imperial units are defined exactly in terms of SI units: 1 inch = 0.0254 m, 1 foot = 0.3048 m, 1 mile = 1,609.344 m, 1 pound = 0.45359237 kg, and 1 standard atmosphere = 101,325 Pa.

4. Why Fuel Economy (L/100 km ↔ MPG) Is Inverse, Not Linear

European fuel consumption (L/100 km) measures volume per distance, whereas US/UK fuel economy (mpg) measures distance per volume. Their relationship is reciprocal: MPG (US) = 235.214583 ÷ (L/100 km) and MPG (UK) = 282.480936 ÷ (L/100 km).

5. Decimal vs. Binary Data Prefixes (MB vs. MiB)

SI decimal prefixes use powers of 10 (1 GB = 1,000,000,000 bytes), while IEC binary prefixes use powers of 2 (1 GiB = 1,073,741,824 bytes). EveryUnit includes both decimal and binary units in the Data Storage converter.