How do I convert PM times to the 24-hour clock?

Add twelve to the hour and drop the suffix, so 7:30 PM becomes 1930 and 11:15 PM becomes 2315. The minutes never change. The single exception is noon: 12:00 PM is already 1200 and adding twelve to it would produce a time that does not exist.

What is 12:00 AM in military time?

12:00 AM is 0000, midnight at the start of a day. It is the second of the two exceptions to the add-twelve rule, because 12 AM becomes 00 rather than keeping its number. The same instant can be written 2400 when it marks the end of the previous day.

Do I add twelve to morning times?

No. Morning hours keep their number and simply gain a leading zero, so 6:15 AM becomes 0615 and 9:00 AM becomes 0900. Adding twelve applies only to afternoon and evening times. Applying it to a morning hour is the most common conversion error by a wide margin.

Is there a quick way to check a conversion?

Yes. Any four-digit result below 1200 should have come from an AM time, and anything from 1300 upward should have come from a PM time. If a morning appointment has converted into a figure in the twenties, the add-twelve rule has been applied where it did not belong.

Convert AM PM to Military Time

Most people learn to convert AM PM to military time twice: once badly, from a half-remembered rule, and once properly, after a missed appointment. The proper version takes one sentence. Add twelve to any afternoon or evening hour, leave morning hours alone, and remember that noon and midnight are the two places the rule does not apply. Everything else about the conversion is practice.

This guide sets out the rule, the two exceptions, a mental method that survives distraction, and the checks that catch a wrong answer before it reaches a form. If you would rather have the arithmetic done for you, the military time converter handles both directions instantly, and the same conversion appears row by row on the full military time chart.

How Do You Convert AM PM to Military Time?

Add twelve to the hour for any PM time and keep the hour for any AM time, then write the result as four digits with the minutes unchanged. 3:45 PM becomes 1545 and 6:05 AM becomes 0605. The suffix is discarded, never carried across.

Three points make this reliable rather than merely correct. The minutes never change, so only ever touch the hour. The result is always four digits, which means a morning hour needs a leading zero to fill the space. And the suffix disappears completely: writing 1545 PM is not a belt-and-braces clarification, it is a contradiction, since the 15 has already said everything PM could say.

What Are the Two Exceptions?

Noon and midnight break the rule because the 12-hour clock uses the number twelve for both of them. 12:00 PM is 1200 with nothing added, and 12:00 AM is 0000 rather than 1200.

12:00 PM, noon: becomes 1200. Adding twelve would produce 2400, which is midnight, twelve hours out.
12:00 AM, midnight: becomes 0000. The hour drops to zero instead of keeping its number.
12:30 PM: becomes 1230, following the noon rule. The half hour after midday is where most people slip.
12:30 AM: becomes 0030, following the midnight rule, and belongs to the date that has just begun.

Midnight carries a further wrinkle, since the same instant may legitimately be written 2400 when it closes a period rather than opening one. That distinction is set out in is midnight 0000 or 2400, and it matters on any timesheet or dispatch log covering a night shift.

Convert AM PM to Military Time in Your Head

Work in two steps and never in one. First decide which half of the day you are in, then apply the single operation that half requires, and only afterwards write the digits down.

For PM hours the addition is easier as a subtraction in disguise: rather than adding twelve to seven, think of the evening hours as counting on from twelve, so seven in the evening is the seventh hour after noon and lands on nineteen. For hours from one to seven in the afternoon, adding twelve is quick enough to do directly. For eight, nine, ten and eleven in the evening, the results are worth memorising outright as 2000, 2100, 2200 and 2300, since they come up constantly and the arithmetic offers no advantage. Morning hours need no thought beyond the leading zero, which is why the whole method reduces to a single question asked first: morning or not.

Worked Examples

Five conversions cover every shape the rule can take, and working through them in order is quicker than reading another explanation:

7:15 AM: a morning hour, so keep the seven, add the leading zero and copy the minutes. The military time equivalent is 0715.
11:50 AM: still morning, and the last hour before the rule changes. It becomes 1150.
12:20 PM: the noon exception, so the hour stays at twelve and the answer is 1220 rather than 2420.
4:05 PM: an afternoon hour, so four plus twelve gives sixteen and the answer is 1605 with the zero in the minutes preserved.
12:45 AM: the midnight exception, so the hour drops to zero and the answer is 0045 on the date that has just started.

The pattern to notice is that only the first two digits ever move. Anyone who finds themselves altering the minutes has misunderstood the rule rather than miscalculated it, and the underlying structure of the four digits is worth revisiting in how to read military time before going further.

Converting Back the Other Way

Reverse the rule and subtract twelve from any hour of 1300 or above, then add PM. 1845 becomes 6:45 PM, while 0645 keeps its number and becomes 6:45 AM once the leading zero is dropped.

The exceptions mirror themselves too. 1200 becomes 12:00 PM and 0000 becomes 12:00 AM, and neither one obeys the subtraction. The hour-by-hour military time chart lays out both directions in one table, which is useful while the pattern is still settling.

Checks That Catch a Wrong Answer

Two checks catch nearly every conversion error, and both take a second. Any result below 1200 must have come from an AM time, and any result from 1300 upward must have come from a PM time; if that does not hold, the rule has been applied to the wrong half of the day.

Adding twelve to a morning hour: 9:00 AM is 0900, not 2100. This is the most frequent mistake by a wide margin.
Adding twelve to noon: 12:00 PM is 1200. Producing 2400 here moves a lunchtime meeting to the middle of the night.
Changing the minutes: the minute field is copied across untouched, since both systems count minutes from 00 to 59.
Dropping the leading zero: 0700 written as 700 breaks the fixed-width format that lets a column of times sort and align correctly.
Keeping the suffix: a converted time never carries AM or PM, in the same way that an ISO 8601 timestamp never does.

These are worth rehearsing because the settings that use military time are the ones where an error is expensive. A medication administration record, an aviation flight plan, a railway timetable and a payroll timesheet are all built on the assumption that whoever wrote the time converted it correctly, and none of them offers a second chance to check.

Conclusion

To convert AM PM to military time, add twelve to afternoon and evening hours, leave morning hours alone with a leading zero, and treat noon as 1200 and midnight as 0000. Copy the minutes across untouched and drop the suffix entirely. Two checks confirm the answer before it goes anywhere near a form. Try it against the 24-hour time converter, watch the format run live on the military time now clock, or explore the rest of militarytime.now.

Convert AM PM to Military Time: The Rule and Two Exceptions