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20 original, in-depth pieces on how measurement systems work, where they came from, and the places conversion quietly goes wrong. Written for this site, not syndicated from anywhere.
Case Studies
1 articlesMeasurement Systems
5 articlesMetric vs Imperial: Why the United States Never Switched
The US signed the Metre Convention in 1875 and has legally defined its inch in metric terms since 1959. So why does it still sell milk in gallons?
The History of the Metre: From the Earth's Quadrant to the Speed of Light
The metre has been defined four different ways in 230 years. Each redefinition solved a problem the previous one created.
How the Kilogram Was Redefined in 2019 (And Why It Had To Be)
For 130 years the kilogram was a lump of metal in a vault near Paris. Then it started losing weight — and nobody could prove it.
Why a US Gallon Is Not a UK Gallon (And What Else Differs)
The US and UK gallons differ by about 20%. The pint, the fluid ounce and the ton diverge too — and the fluid ounce diverges in the opposite direction.
Celsius, Fahrenheit and Kelvin: Which Scale to Use and Why
Three temperature scales, three different zero points. Understanding what each zero represents explains why temperature conversion is not simple multiplication.
Practical Guides
5 articlesSignificant Figures: Why Your Converter Shows More Digits Than You Should Use
A calculator will happily give you fourteen decimal places for a measurement you made with a tape measure. Here is how to know which digits mean anything.
Why Your 1 TB Drive Shows 931 GB: The GB vs GiB Problem
Your drive is not lying and neither is your operating system. They are using two different definitions of the same word.
Cooking Conversions: Why Professionals Weigh Everything
A cup of flour can vary by 30% depending on how you fill it. Here is why volume measurement fails in baking and how to convert recipes reliably.
MPG vs L/100km: The Inverse Relationship That Fools Everyone
Improving from 10 to 20 MPG saves more fuel than improving from 30 to 60 MPG. This is not a trick — it is what happens when you average a reciprocal.
Density and Specific Gravity: Converting Between Weight and Volume
There is no universal conversion between litres and kilograms. Density is the missing variable, and it changes with temperature.
Technical Reference
9 articlesPressure Units Explained: PSI, Bar, Pascal and Why Gauge Is Not Absolute
Your tyre gauge reads 32 PSI but the air inside is at about 47 PSI absolute. Understanding the difference matters more than the conversion factor.
Nautical Miles and Knots: Why Ships and Aircraft Use Their Own Distance Unit
A nautical mile is not an arbitrary imperial survival. It is one minute of latitude, which makes navigation arithmetic work on a sphere.
Horsepower: Why There Are At Least Four Different Kinds
Mechanical, metric, electrical and boiler horsepower are all different. The gap between the common two is about 1.4%, and it is why European and American figures never quite match.
Volts, Amps, Watts and Ohms: What Each One Actually Measures
The water-pipe analogy gets you started but breaks down fast. Here is what each electrical unit means and how they connect.
Torque Specifications: Newton-Metres, Foot-Pounds and Why Direction Matters
Torque converts simply between units, but applying it correctly involves more than the number — including why a torque wrench extension changes the reading.
Lumens, Lux and Candela: Buying Lighting Without Being Misled
Three units describe light output, and manufacturers pick whichever flatters the product. Here is what each one actually measures.
Becquerel, Gray and Sievert: Three Radiation Units That Are Not Interchangeable
One measures how much a source decays, one measures energy absorbed, one measures biological harm. News reports routinely mix them up.
Points, Picas, Pixels and Ems: Typography Units Explained
A point has been at least four different sizes. Understanding which one your software uses explains a lot of print and web layout confusion.
Degrees, Radians and Gradians: Which Angle Unit and Why
Degrees are convenient, radians are mathematically natural, gradians were a metric experiment that mostly failed. The distinction matters in code.