Guides

Short guides on the questions behind the tools. Each one explains how something works, with figures taken from the tools and their sources, and links to the tools that do the job.

• Audio Bitrate and File Size: How Big Will It Be?

  How to work out the size of an MP3, M4A or WAV file from its bitrate and length, why a lower bitrate makes the file small, and when lossless is worth it.

• Date Math Traps: Month Ends, Leap Years, Weeks

  Why January 31 plus one month is February 28, how to count days between dates, what a leap day does to anniversaries, and how ISO weeks are numbered.

• Exact Unit Conversions Worth Knowing

  The inch, foot, mile and Fahrenheit conversions that are exact by definition, the pound and the Korean pyeong, with worked examples you can check.

• JPG, PNG, WebP or AVIF: Which Image Format to Use

  How JPG, PNG, WebP and AVIF differ in size, quality, transparency and browser support, and which one to pick for photos, screenshots and logos.

• Why Text Turns Garbled: Encodings and Mojibake

  Why é becomes é and 안녕 becomes 안녕, what a wrong encoding does to the bytes, when garbled text can be repaired and when it cannot.