Measurement guides
A converter gives you a number. These guides explain the thing behind the number — why two gallons exist, why a terabyte drive shows up smaller than advertised, and when a rounded answer stops being good enough. 12 guides, each written to answer one question properly.
Written and maintained by the UnitFlip Editorial Team. Every guide cites the standards it draws on and carries the date it was last reviewed.
Systems & standards
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Metric System vs Imperial System
How the two systems relate, who uses what, and why every Imperial unit is now legally defined in metric terms.
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Weight vs Mass: What Is the Difference?
Why your scale reads kilograms even though it is measuring a force — and when that shortcut breaks.
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Celsius, Fahrenheit and Kelvin Explained
Three scales, two offsets, one degree size shared between two of them.
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SI Units: A Practical Guide
Seven base units, one 2019 redefinition, and the writing rules almost everyone gets wrong.
Everyday measures
Digital & media
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MB, GB, MiB and GiB Explained
The missing 7% on every hard drive, explained by two definitions of 'giga'.
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Mbps vs MB/s and Download Speed
Divide by eight — then explain the rest of the gap with protocol overhead.
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DPI vs PPI Explained
Same arithmetic, different machines — and the one place mixing them ruins a print.
Technical
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PSI, Bar and kPa Pressure Guide
Three units, one quantity, and the gauge-versus-absolute distinction that catches people out.
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MPG vs L/100km Fuel Economy Guide
Reciprocal units, the MPG illusion, and the two different gallons hiding in the same abbreviation.
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Significant Figures and Rounding in Unit Conversion
Converting 3 inches does not give you 76.2 mm of certainty — here is how to report it honestly.
Looking for a converter instead?
Every guide links to the tools it discusses, but you can also go straight to all converters by category, the everyday tools for cooking, height and sizes, or read how the conversions are calculated and verified.