Measure typing speed in words per minute from a sample.
Typing tests standardise a word at five keystrokes including spaces, so gross speed is characters divided by five, divided by minutes. Net speed subtracts one word per uncorrected error per minute — the convention used by every serious typing assessment, and the reason a fast, sloppy run can score below a slower accurate one. Reporting both plus accuracy separates the two skills, since improving accuracy is usually the faster route to a better net score than pushing raw speed.
Gross speed
Gross wpm = (characters / 5) / minutes
Net speed
Net wpm = gross wpm - (uncorrected errors / minutes), floored at zero
Around 40 net wpm is average for an office worker, 65 to 80 is fast, and above 100 is exceptional. Professional transcription roles typically require 60 to 75 net with accuracy above 98 percent.
Because a mistake costs more than the keystroke — it must be found and repaired, and in real work an uncorrected error can cost far more than that. The one-word penalty is a deliberately blunt proxy for that cost.