
Three minutes is a common length for typing tests at school and in job applications. Type a random passage for three minutes and get your words per minute and accuracy as soon as time is up.
It's long enough that you can't coast on a burst of speed, but short enough to stay focused the whole way through. That's why many typing classes and employers use tests of around three to five minutes when they want a realistic number.
Start at a pace you can hold instead of sprinting — speed that collapses after the first minute costs more than it gains. Keep your eyes on the text, correct mistakes quickly and keep going, and don't stop to check the timer.