Convert 12-Hour to 24-Hour Time Online
Convert 12-hour AM/PM time to 24-hour military format - hours, minutes, and optional seconds. Free, client-side, instant, offline, secure.
Enter an AM/PM time and see it instantly in 24-hour military format — hours, minutes, and optional seconds, with a copy-ready result.
How to Use Convert 12-Hour to 24-Hour Time Online
- Enter the hour (1-12) in the Hours field. Any value outside that range triggers an inline error naming the problem - the output keeps the last valid result so you never lose your place.
- Enter the minutes (0-59) in the Minutes field. The result recomputes instantly on every keystroke - no need to click Convert to see the number change.
- Pick AM or PM from the Meridian dropdown. 12:00 AM becomes 00:00 (midnight is hour zero), 12:00 PM stays 12:00 (noon keeps its number), and everything between 1 PM and 11 PM gets the classic +12 offset.
- Tick "Include seconds" if you need
HH:MM:SSoutput. A Seconds input appears next to the toggle, validates 0-59, and the result gains the third component automatically. - Read the stats line - it echoes the canonical 12-hour source (for example
3:07 PM) alongside the 24-hour output15:07, so you can double-check at a glance. - Copy writes the 24-hour string to the clipboard, or Download .txt saves a small file with both the source and the result - useful for logging or evidence in tickets.
- Press
Ctrl+Enter(⌘+Enteron Mac) to re-run the conversion and copy the result in a single shortcut. Clear and Reset both return the tool to the default 12:00 PM starting point.
Frequently asked questions
Is my time data secure when converting?
Yes. The conversion is a few integer operations performed in your browser – nothing is uploaded, cached, or tracked. After the page loads you can disconnect the network and keep converting indefinitely.
Is this time converter free to use?
Yes, completely free with no limitations. No sign-up, no usage cap, no hidden fees. Convert as many times as you like.
Does this work offline without internet?
Yes. Once the page loads, the tool runs entirely offline. No network connection is required – perfect for air-gapped or locked-down environments.
How does 12-hour to 24-hour conversion work?
AM times keep their hour, except 12 AM which becomes 00. PM times add 12 hours, except 12 PM which stays 12. Minutes and seconds never change – only the hour is transformed.
What is 12:00 AM in 24-hour format?
12:00 AM (midnight) is 00:00 – the first minute of the new day. The tool handles this edge case explicitly via the mod-12 rule.
What is 12:00 PM in military time?
12:00 PM (noon) stays 12:00. Unlike midnight, noon keeps the same hour digit in both formats.
Why use 24-hour military time?
It removes AM/PM ambiguity, is standard in military, medical, aviation, and international contexts, makes time arithmetic easier (no “does it roll over?” guesswork), and dominates everywhere outside the United States.
Can I convert times that include seconds?
Yes. Tick the “Include seconds” toggle and a Seconds field (0-59) appears. The output switches to HH:MM:SS and the stats line mirrors the same precision, so 3:07:09 PM renders as 15:07:09.
Which browsers support this converter?
Every modern browser: Chrome, Firefox, Safari, Edge, Opera, plus mobile browsers on iOS and Android. JavaScript is the only requirement and it is enabled by default everywhere.
How do I convert 24-hour back to 12-hour?
Use the sibling 24-Hour to 12-Hour Time Converter – the conversion is exact and fully reversible with no data loss in either direction.