12-Hour to 24-Hour Time Converter

3:40 PM is 15:40, and 15:40 is 3:40 PM

The 12-hour clock counts the morning and the afternoon separately, each up to 12, and adds AM or PM. The 24-hour clock counts straight through from 0 to 23. To turn a PM time into 24-hour time, add 12 to the hour. To turn 13 to 23 back into 12-hour time, subtract 12 and add PM. The minutes and seconds never change.

The only tricky hour is 12. Midnight is hour 0 in 24-hour time and is usually written 12:00 AM. Noon is hour 12 in 24-hour time and is written 12:00 PM. Type any time into the converter above, such as "3:40 PM", "15:40", "1540", "11 at night" or "noon", and it shows the other notation, the rule it applied and the way you would say the time aloud. Military time, the 24-hour time written without a colon (1540), is shown too.

When you need to switch between the two

The same time is written differently depending on who wrote it, so you often have to translate when you copy it somewhere else. Typical cases:

• Moving a booking into a calendar: an appointment text says "3:40 PM", while a work calendar, a booking system or a spreadsheet may use a 24-hour column and expect 15:40.
• Reading timetables: many train, ferry and airline schedules print 19:05 with no AM or PM. You have to read it as 7:05 PM straight away to avoid planning the evening around the wrong departure.
• Setting up devices and apps: phones, watches, smart-home timers and alarm apps let you choose a 12-hour or 24-hour display, and a schedule you type in the wrong notation can end up twelve hours off.
• Building shift rotas: a night shift crosses midnight, and writing it as 22:00 to 06:00 makes it clear where the date changes. The bulk converter lets you convert a whole rota in one go.
• Travel and business writing: a 24-hour time such as 14:00 in an itinerary, a meeting invitation or a report leaves no room for an AM/PM mix-up, especially between people who are used to different conventions.

How to use the converter

1. Type a time into the top box. It reads "3:40 PM", "3:40 pm", "15:40", "1540", "0800 hrs" and wording such as "7 in the evening". The "Now" button inserts the time on your device.
2. The large result shows the other notation: type 12-hour time and you get 24-hour time, and the other way round. Under it, a line such as "3 PM → 3 + 12 = 15" shows the rule that was applied.
3. If you type "3:40" with no AM or PM, it is read as 24-hour time (03:40), and a "Read it as 3:40 PM" button offers the other reading. Press the one that matches what the original meant.
4. The rows below list the same time as "12-hour", "24-hour", "Military time" and "In words". Each row has its own "Copy" button, and "Copy both on one line" gives you something like "3:40 PM = 15:40". The clock face shows the same hand against an inner 1 to 12 ring for 12-hour time and an outer 13 to 23 and 00 ring for 24-hour time.
5. In the "24-hour chart", tap an hour to jump to it. The minutes stay as they are. The small number on each cell is the 12-hour hour and the large number is the 24-hour hour.
6. For a schedule or a rota, open "Convert many times at once" and paste your text. The words stay, only the times change, and you can choose "All 24-hour" or "All 12-hour" and copy the result.

The conversion rule

Four rows are enough. Remember 12 and 0 separately, and everything else is adding or subtracting 12.

Going the other way, 00 becomes 12 AM, 01 to 11 stay AM, 12 becomes 12 PM, and 13 to 23 have 12 taken off and PM added. For example, 21:30 is 21 − 12 = 9, so 9:30 PM.

24-hour conversion table

Every full hour in three forms. The "spoken form" column follows the day periods described in the section on period words. When minutes are present, convert only the hour with this table and keep the minutes.

Midnight, noon, 12 AM and 12 PM

Noon and midnight are the two points where AM and PM meet, which is why "12 AM" and "12 PM" cause so much confusion. In everyday use, 12 AM is read as midnight, the start of the day, and 12 PM as noon. This converter reads them the same way: 12 AM is hour 0 and 12 PM is hour 12. For example, 12:30 AM becomes 00:30 and 12:30 PM stays 12:30.

Not everyone agrees on this, so official guidance avoids the labels. The US National Institute of Standards and Technology (NIST) says in its Times of Day FAQs that 12 a.m. and 12 p.m. are ambiguous and should not be used, and that since noon is neither before noon nor after noon, a designation of either a.m. or p.m. is incorrect. For midnight it points to 0000 for the beginning of a given day and 2400 for the end of a day, and it says that giving an event as 11:59 p.m. or 12:01 a.m. on a particular day is a good idea. The converter follows that advice by showing a note whenever you enter 12 AM or 12 PM, and its output for the hour itself says "midnight (12:00 AM)" or "noon (12:00 PM)".

"Midnight tonight" is where dates go wrong. If a deadline is "midnight on Friday", people may mean the end of Friday, which is 00:00 on Saturday, or the start of Friday. Writing the date with 23:59 (for example "Friday 23:59") removes the doubt, and the converter explains the difference when you type "midnight".

Period words: morning, afternoon, evening, night

In speech we often add a word instead of AM or PM. The input box understands "in the morning", "in the afternoon", "in the evening", "at night", "noon", "midday" and "midnight", as well as "am", "pm", "a.m." and "p.m.". "7 in the evening" is 19:00, "9 at night" is 21:00 and "2 in the afternoon" is 14:00. "12 at night" is read as midnight, which is 00:00, and "1 to 5 at night" is read as the small hours after midnight, so 2 at night is 02:00 and the converter notes that the date may be the next day.

The "In words" row and the table's spoken form use the English day periods in Unicode CLDR 48: from 00:00 morning, from 12:00 afternoon, from 18:00 evening and from 21:00 night. Real usage varies from person to person, and many people say "2 at night" for 02:00, which CLDR calls morning. These ranges are a display convention, not a rule.

Military time (1540 and 0800 hrs)

"Military time" in everyday English means 24-hour time written without a colon: four digits, with the first two for the hour and the last two for the minutes. 3:40 PM is 1540, usually said "fifteen forty", and 8:00 AM is 0800. The converter's "Military time" row shows this form, and its input box also accepts 1540, "1540 hours", "0800 hrs" and "1540h". The number is simply the 24-hour time without the colon, so you convert it exactly as you would 15:40.

This is useful when you are reading a roster, a flight schedule or a log that prints times as four digits. 0030 is 12:30 AM, 1200 is noon and 2359 is 11:59 PM. Because the converter treats 24:00 as the end of the day, it shows 24:00 as 00:00 of the next day, and 0000 as the start of a day.

Common mistakes

• Adding 12 to 12 PM: 12:30 PM written as 24:30 is wrong. Noon takes no 12, so it is 12:30.
• Writing 12:10 AM as 12:10: 12:10 AM is just after midnight, which is 00:10. Writing 12:10 turns it into a midday time.
• Leaving the date off a midnight deadline: "midnight Friday" can mean either end of the day. Give the date and the 24-hour time, for example Friday 23:59.
• Sending "3:40" without AM or PM: the reader has to guess between 03:40 and 15:40. If you write 12-hour time, always include AM or PM.
• Mixing both notations, such as "15:40 PM": AM and PM belong only to the 12-hour clock. Write either 15:40 or 3:40 PM. The converter reports this as an error.

Limits and caveats

• The tool only changes the notation of the same moment in the same place. It does not convert between time zones or handle daylight saving time, so use a time-zone converter to find out what 15:40 in one city is somewhere else.
• It does not take dates. Hours 24 to 47 are converted and marked "Next day", but it does not carry a real date forward. Hours of 48 and above are rejected.
• Ambiguous input, such as "2 at night" or a bare 1 to 12 with no AM or PM, is read by a fixed rule and the converter tells you it did so. Ask the person who wrote the time what they meant.
• The spoken form is a display convention based on CLDR day periods, and people in different places say it differently.
• The bulk converter changes only text that looks like a time, such as "3:40 PM", "15:40" or "1540 hours" (a bare four-digit number like 1540 is left alone in bulk text, because it could be a year or a code). It skips lengths like "3 hours" and dates, but it may convert another number that looks like a time, for example a score of 2:15 or a ratio of 1:10. Most of these carry no AM or PM, so they get a dotted underline; read the result through once.
• Only whole seconds are accepted. Fractions of a second are not handled.

Sources

• 01NIST: Times of Day FAQs12 a.m. and 12 p.m. are ambiguous and should not be used; 0000 is the beginning of a day and 2400 the end; 11:59 p.m. and 12:01 a.m. are a good way to specify the day
• 02Unicode CLDR 48: Day PeriodsEnglish day periods: 00 morning, 12 afternoon, 18 evening, 21 night
• 03National Astronomical Observatory of Japan: FAQ 4-1 (in Japanese)Shows that the labels for 12 o'clock can differ by country: Japan's 1872 time table wrote noon only as 午前12時

Sources checked 2026-10-20.

Frequently asked questions

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