Countdown
Timer
Set a timer for any amount of time
Quick presets
How does a countdown timer work?
A countdown timer works by recording a target duration and continuously subtracting elapsed time from it. When you start a five-minute timer, the tool stores 300 seconds as your target and decrements the display every second until it reaches zero. At that point it typically sounds an alarm or shows a visual alert to let you know time is up.
Clockr uses the browser's performance API for accurate millisecond timing rather than relying on setInterval alone, which can drift when the browser is busy or a tab is in the background. By anchoring each tick to a high-resolution timestamp, the timer stays aligned with real elapsed time even if individual interval callbacks fire slightly late.
Countdown timers have countless practical uses. In the kitchen they track boiling eggs, baking times, and rest periods between recipe steps. For exercise they structure work and rest intervals in HIIT workouts. Speakers use them to stay within presentation time limits, and students use the Pomodoro technique — typically 25 minutes of focused study followed by a short break — to maintain concentration throughout the day.
Frequently asked questions
What is the Pomodoro technique and how long should the timer be?
The Pomodoro technique is a time-management method developed by Francesco Cirillo in the late 1980s. You work in focused 25-minute blocks called "pomodoros", separated by 5-minute breaks. After four pomodoros, take a longer break of 15 to 30 minutes. Set Clockr to 25 minutes for each work session and 5 minutes for short breaks — the preset buttons make this quick to start.
How do I use a timer for exercise intervals?
For interval training, alternate between work and rest periods using the timer. A common HIIT pattern is 40 seconds of intense exercise followed by 20 seconds of rest, repeated for several rounds. Set the timer to your work duration, start it when you begin, and reset or adjust for the rest period when it sounds. The +1 Min button lets you extend a round without restarting from scratch.
What is the best timer length for studying?
Research suggests focused study blocks of 25 to 50 minutes work well for most people, with a 5 to 10 minute break between sessions. The Pomodoro technique uses 25 minutes; some students prefer 45 or 50 minutes for deeper work before a longer break. Experiment to find what keeps you focused without mental fatigue — Clockr's presets from 15 to 45 minutes are a good starting point.
How accurate is an online countdown timer?
Online timers are accurate to within a fraction of a second when the browser tab is active. Clockr uses high-resolution timing via the performance API to minimise drift. Accuracy can decrease if the tab is heavily throttled in the background, but for typical use — cooking, studying, exercising — the timer is more than precise enough.
Can I use a countdown timer without an internet connection?
Yes. Once the Clockr page has loaded in your browser, the countdown timer runs entirely in JavaScript on your device — no server connection is needed. If you have visited the page before, your browser may have cached it so it works offline. Keep the tab open while the timer is running for the most reliable experience.
What is an interval timer and how is it different from a countdown timer?
A countdown timer counts down from a set duration to zero and stops. An interval timer automatically alternates between work and rest periods for multiple rounds — for example, 30 seconds on, 10 seconds off, repeated eight times. Clockr is a countdown timer; you can simulate intervals by resetting or adjusting the time between rounds manually.
How do I time a presentation?
Set the timer to your allotted speaking time — for example, 10 or 20 minutes — and place the browser window where you can glance at it without distracting the audience. Start the timer when you begin speaking. When two to three minutes remain, mentally wrap up your key points. The alarm at zero is your hard stop. Practise with the timer beforehand so you know how much content fits your slot.
What is the longest countdown timer ever used?
There is no official record for the longest countdown timer, but extraordinary examples abound. Space agencies use multi-year countdowns for mission launches. The Doomsday Clock, maintained since 1947, metaphorically counts down humanity's proximity to catastrophe. For everyday use, Clockr supports timers up to 99 hours — enough for even the most ambitious cooking projects.