45 minutes timer

What a 45-minute timer is good for

Forty-five minutes is the length of a school class period, a university lecture, a typical therapy session, and a popular extended-focus work block. It maps neatly onto the natural rhythm of adult attention, which tends to wane somewhere between forty-five and ninety minutes of sustained concentration, making it a sustainable interval for genuinely deep work.

• •A school class period or lecture block
• •An extended deep-work or study session
• •A standard 50-minute therapy hour, trimmed to focused time
• •A full fitness class or long training session
• •Exam practice sections timed to the real paper

Working with your attention span, not against it

The forty-five-minute block sits inside a well-documented pattern in how attention works. Concentration is not a flat resource you can spend evenly across a day; it rises, peaks, and decays in cycles, and for most adults a single uninterrupted stretch of high-quality focus lasts somewhere between forty-five and ninety minutes before returning diminishes. Schools and universities settled on forty-five-to-fifty-minute periods through a century of trial and error for exactly this reason — it is long enough to develop an idea but stops before the class glazes over. For your own work, a forty-five-minute timer is a good 'medium' setting: longer than a Pomodoro, so you can get into something complex that needs a running start, but bounded so that you take a real break before fatigue quietly turns the last fifteen minutes into low-value busywork. Follow it with a proper ten-to-fifteen-minute break, away from the screen, and the next block starts fresh rather than already depleted.

How this 45-minute timer stays accurate

Most browser timers drift, because they count by accumulating small ticks, and browsers deliberately slow those ticks down in background tabs to save battery. This one is different: the moment you press start it records the exact wall-clock time the countdown should end, and every frame it simply measures how long is left until that fixed end time. If you switch tabs, lock your phone, or the tab is throttled, the remaining time is recomputed from the real clock the instant you come back, so a 45-minute timer is still a 45 minutes timer rather than however long the throttled ticks happened to add up to. On phones the page asks for a screen wake lock while the countdown is running, where the browser allows it, so the display does not sleep mid-count. The alarm is synthesised in the browser with the Web Audio API, which means there is no audio file to download and the chime is ready the moment you start.

Other timer lengths

Need a different length? These are the timers people most often reach for alongside a 45-minute timer:

• 30 minutes timer
• 1 hour timer
• 90 minutes timer

Frequently asked questions

Why are classes and lectures often 45 minutes?

Forty-five to fifty minutes matches the span over which most people can sustain high-quality attention before it declines. It is long enough to teach a complete idea and short enough to end before the room loses focus.

Is 45 minutes good for deep work?

Yes, for many people it is the sweet spot — longer than a 25-minute Pomodoro so you can tackle something complex, but bounded so you rest before fatigue sets in. Take a 10-to-15-minute break afterwards before the next block.

Can I use this to time exam practice?

Yes. Set the timer to match the section you are practising and treat the alarm as a hard stop, just like the real exam. It builds the pacing instinct you need under timed conditions.

Does the 45-minute timer work offline?

Yes. Once the page has loaded, the countdown runs entirely in your browser using your device clock, so it keeps working with no connection. The alarm is generated in the browser too, so there is no sound file to download.