12 Hour Timer

Press Start to count down 12 hours.

This free 12 hour timer counts down 12 hours with a shrinking red disc you can read at a glance. 12 hours is 43,200 seconds (forty-three thousand two hundred seconds), or 720 minutes. It covers an intermittent fast, an overnight dough prove and a long shift.

Share:WhatsAppXReddit

Nearby timers

What a 12 hour timer is good for

Twelve hours is half a day. The simplest form of intermittent fasting is a twelve hour overnight fast, and many bakers leave dough to prove slowly in the fridge for about twelve hours.

A 12:12 fast

Stop eating after dinner and start again twelve hours later, the gentlest form of time-restricted eating.

An overnight prove

Pizza and bread dough left in the fridge for twelve hours develops more flavour.

A long shift

Nurses and other shift workers often work twelve hour shifts.

A half-day event

Use it to count down to an event later the same day.

To pace yourself, glance at the disc rather than the numbers. With the 12 hour timer running, half the colour has gone after 6 hours, and when only a quarter is left you have 3 hours to wrap up. Open fullscreen if the timer needs to be read across a room, and add a label so everyone knows what the 12 hours are for.

How to use the 12 hour timer

  1. It is ready

    The dial is already set to 12 hours. To change it, drag the disc, tap a preset or open Custom.

  2. Press Start

    Or press the Space bar. The red disc shrinks back towards 12 o’clock as the time runs down.

  3. Watch the disc

    Read the time left at a glance, or open fullscreen for a big dial that fills the screen.

  4. Time’s up

    Your alarm plays until you press Stop. Press Reset or R to run the same time again.

12 hours in other units

12 hours equals
Seconds43,200
Minutes720
Hours12
Days0.5
Fraction of a day1/2

Why use this timer

Why a visual timer helps

A shrinking disc turns time into something you can see. You read how much is left at a glance, without doing sums on a clock, and an invisible deadline feels less stressful when you can watch it approach. That is why visual timers are a staple in classrooms and are widely used by people with ADHD and autistic children and adults. Read our guide to using a visual timer, how it helps with ADHD time blindness, classroom transitions and autism.

Why this timer is accurate

The countdown is anchored to your device clock rather than counted in animation frames. It does not drift if you switch tabs or your screen sleeps: it keeps running in the background and still sounds the alarm on time. When you come back, the disc jumps straight to the correct position.

Frequently asked questions

There are 43,200 seconds in 12 hours, which is 720 minutes.

A twelve hour overnight fast, a slow fridge prove for bread or pizza dough, a long work shift, or counting down to an event later the same day.

Yes. The 12 hour countdown is anchored to your device clock rather than counted frame by frame, so it stays accurate in a background tab and the alarm still fires when the 12 hours are up.

No. The 12 hour timer runs in your browser on phone, tablet and desktop. It is free, and there is no account, app or download.

Yes. Press the fullscreen button or the F key. The dial fills the screen, so the remaining part of the 12 hours is readable from the back of the room.

Yes, once this page has loaded. Nothing is sent over the network while the 12 hours count down, so a dropped connection will not stop the timer.

Seven hundred and twenty minutes, which is 43,200 seconds.

When the 12 hours are up the disc is empty, the screen shows Time’s up! and your alarm plays until you press Stop. It stops by itself after five minutes.

More timers