45 Minute Timer

Forty-five minutes is a slot in someone's calendar

Most timer lengths are chosen by the person setting them. Forty-five minutes usually is not. It is the length of a school period, a coaching or therapy hour that politely is not one, a driving lesson, a gym class. Somebody else decided it, which changes what you need from a countdown: not a nudge to keep going, but a reliable mark for a block that has to end on time because the next one starts.

• A lesson or seminar period, with the clock visible to the room
• A coaching, therapy or tutoring session that bills by the slot
• A gym class, a long run, or a full circuit
• One section of a practice exam under timed conditions
• A deep-work block long enough to reach the difficult part
• A rehearsal or practice session with a fixed finish

Running a lesson or a session with it on screen

When the countdown is for a room rather than for you, readability beats everything else. Tap the fullscreen icon and the digits fill the whole display, which is what you want on a projector or an interactive whiteboard where the back row is eight metres away. The students stop asking how long is left, because they can see it. If you teach with this regularly, the classroom timer page is the same tool with presets chosen for group work, tests and transitions rather than for a single forty-five minute block.

Keeping a long block honest when you get interrupted

Over forty-five minutes something will interrupt you. A knock, a question, a fire drill. Pause holds the exact remaining time and Resume continues from that second, which matters more here than on a short countdown: restarting a five-minute timer costs you five minutes, restarting a forty-five minute one costs you most of an afternoon. Use it honestly and the number on screen stays the truth about how much of the session is left.

What happens at the forty-five minute mark

A two-tone beep plays three times and the message appears on screen. The sound is generated in the browser rather than loaded from a file, so it works offline once the page is open, and the speaker icon turns it off in advance if you are running a silent test. One caveat worth knowing before you rely on it for something scheduled: the tab has to stay open. Close it and the countdown goes with it, because there is no server keeping time on your behalf.

Leaving it running in a background tab

Forty-five minutes is long enough that you will almost certainly switch away, and browsers throttle tabs you are not looking at. A timer built on counting seconds would quietly fall behind. This one works out the clock time the session will end when you press Start, and every update just compares the present moment to that target, so you can spend the whole block in another window and the remaining time will still be exactly right when you look. The tab title carries the countdown too, which is often the fastest way to check.

Shorter and longer slots

Scheduled blocks tend to cluster, so the neighbours either side are the ones worth having to hand: