12 Minute Timer
Set for 12 minutes. Press start — it rings when the time is up.
Free from Ticka — the reminder app that rings like an alarm, even on silent. Close this tab and the timer stops. On your phone, Ticka rings even on silent. App Store → Google Play → App Store → Google Play →
This timer runs while the tab is open. If you need it to go off when your phone is in your pocket — that part needs the app.
Twelve minutes and the Cooper test
In 1968 Kenneth Cooper, a US Air Force physician, needed a fitness test that did not require a lab. His answer was simple: run as far as you can in twelve minutes and measure the distance. The Cooper test is still used by sports clubs, armies and schools because it needs nothing but a track and a timer.
Twelve minutes was chosen to be long enough that sprinting does not pay — you cannot fake the distance with one fast lap — and short enough to finish with something left. That makes it a fair measure of steady effort rather than a burst.
If you run it, run it on a measured loop and write the distance down. The number on its own means little; the same test repeated a month later tells you more than any app summary.