Conversion Guides
Educational content on the theory and practice of unit conversion. Every guide explains the underlying mathematics and cites the primary sources (SI Brochure, NIST SP 811, IEEE 1541).
Foundational Guides
The core concepts behind any unit conversion.
SI vs. Customary Units
How the metric system and imperial/US customary systems differ, and where each is used today.
Significant Figures & Rounding
Why 1 km ≠ 0.6214 mi in every context, and how to round correctly without inflating precision.
Exact vs. Approximate Conversions
Some factors are fixed by definition; others are measured. Knowing which is which prevents subtle errors.
Metric & Imperial Systems
The history of both systems, why the US uses customary units, and how international trade reconciles them.
How to Convert Units Manually
Step-by-step method using dimensional analysis and factor labeling.
Understanding Unit Symbols
Why "m" means meter and "M" means mega, and how to read SI notation correctly.
Subject-Specific Guides
Deeper looks at particular measurement families.
Binary vs. Decimal Data Units
Why a "1 TB" drive shows up as "931 GB" in your OS, and what MiB really means.
Temperature Scales Explained
Celsius, Fahrenheit, Kelvin, and Rankine — how each is defined and where each is used.
Mass vs. Weight
Mass is invariant; weight depends on gravity. Why this distinction matters in physics and everyday life.
Volume Measurement Guide
Liquid vs. dry volume, US vs. imperial measures, and the special problems of cooking conversions.
Area Measurement Guide
Square meters, acres, and hectares — how land is measured in different countries.
Speed Units Explained
km/h, mph, m/s, knots, and Mach — how each is used and why speed limits differ between countries.
Pressure Units Explained
Pascal, bar, psi, atmosphere, torr, and mmHg — where each is used.
Energy Units Explained
Joules, calories, kilowatt-hours, BTUs, and electronvolts — the many faces of energy measurement.
Electrical Units Guide
Volts, amps, ohms, farads, and henries — the fundamental units of electronics.
Digital Storage Guide
From a single bit to a pebibyte — how digital information is measured.
Cooking Measurements Guide
Cups, grams, ounces, and why weighing is more accurate than scooping.
Astronomical Units Guide
AU, light-years, parsecs, and other ways astronomers measure cosmic distances.