TimerStopwatch.com

24 Hour Timer

This free 24 hour timer counts down 24 hours (86,400 seconds) and rings an alarm at zero. It is already set — press Start or the space bar and it begins. It keeps time in a background tab, and full screen makes the digits big enough to read across a room.

24:00:00
Ready

Set the time

Shortcuts Space start / pause R reset F full screen + add a minute Esc stop alarm

24 hours at a glance

Duration24 hours
On the clock24:00:00 (h:mm:ss)
In seconds86,400
In minutes1,440
In hours24
Share of a day100%
Start now, ends at—

What is a 24 hour timer good for?

Twenty-four hours is one full day — a 24-hour challenge, a day-long fast, or a reminder for this exact time tomorrow.

  • Day-long challenges and hackathons
  • 24-hour fasting windows
  • A reminder for the same time tomorrow
  • Curing and setting times

← 12 Hour Timer

How to use the 24 hour timer

  1. Press Start

    The timer is already set to 24 hours. Press Start or Space.

  2. Watch the ring

    The ring empties as time passes, and the tab title counts down with it so you can check from another tab.

  3. Adjust if you need to

    Pause any time, press +1 min to add a minute, or change the time in the panel.

  4. Stop the alarm

    At zero the alarm rings. Press Stop alarm or Esc, or +1 min to snooze.

Other quick timers

One click starts the countdown — every preset rings an alarm, works full screen and keeps time in a background tab.

Seconds

Minutes

Hours

Frequently asked questions

How do I start a 24 hour timer?

Press Start (or the space bar) on this page — the timer is already set to 24 hours. When it reaches zero the alarm rings until you stop it or the ring time you chose runs out.

How many seconds are in 24 hours?

24 hours is 1,440 minutes, or 86,400 seconds.

Will the 24 hour timer ring if I switch tabs?

Yes. The alarm is scheduled ahead on your browser’s audio clock, so background-tab throttling cannot delay it. Turn on notifications in the panel to get a pop-up too. If you reload the page, it keeps counting from where it was.

Can I pause the timer or add more time?

Yes. Pause stops the countdown and Start resumes it. +1 min (or the + key) adds a minute, and after the alarm it starts a one-minute snooze. To set a different length, use the time boxes, the number pad, or one of the other quick timers.

More free timing tools

Online Stopwatch Lap and split times to 1/100 s, best and worst laps, CSV export. Pomodoro Timer 25-minute focus sessions and breaks, with auto-start and a daily tally. Interval Timer HIIT, Tabata, EMOM and boxing rounds with 3-2-1 beeps and voice cues. Countdown to a Date Days, hours, minutes and seconds to any date and time zone, shareable by link. Tabata Timer20 seconds on, 10 seconds off, eight rounds — four minutes, done.

Last reviewed October 31, 2026