12-Hour to 24-Hour Time Converter
Convert any time between the 12-hour AM/PM clock and the 24-hour (military) format, and see the exact seconds since midnight.
Conversion direction
AM or PM
Total seconds elapsed since 00:00
- 1
24-hour hour
(9 mod 12) + 0 = 9mod 12 maps 12 → 0; then add 12 for PM. - 2
Seconds from hours
9 × 3,600 = 32,400 - 3
Seconds from minutes
30 × 60 = 1,800 - 4
Seconds since midnight
32,400 + 1,800 = 34,200
How does this calculator work?
To convert 12-hour to 24-hour time, take the hour mod 12 and add 12 if it is PM, keeping minutes the same and zero-padding to two digits. Reverse the process for 24-hour to 12-hour. This tool also reports the exact seconds since midnight for any entered time.
Formula
How this is calculated
Choose a conversion direction. For 12-hour to 24-hour, enter the hour (1-12), the minute (0-59), and whether the time is AM or PM. The 24-hour hour is computed as (hour mod 12) plus 12 when the period is PM, so 12 AM becomes 00 and 12 PM stays 12. The result is zero-padded to two digits (for example 9:30 AM becomes 09:30).
For 24-hour to 12-hour, enter the hour (0-23) and minute. The period is AM when the hour is below 12, otherwise PM. The displayed 12-hour value is ((hour + 11) mod 12) + 1, which maps 0 to 12 AM and 13 to 1 PM. Both formats are shown side by side.
Seconds since midnight is H24 * 3600 + minute * 60, a useful canonical value for sorting or scheduling. Inputs outside their valid ranges (hour or minute) return no result, and fractional entries are floored to whole units. The converter ignores seconds in the input and assumes a standard 24-hour day.
Frequently asked questions
12 AM is midnight, written as 00:00. 12 PM is noon, written as 12:00.
Add 12 to the hour for any PM time except 12 PM. So 3 PM becomes 15:00 and 11 PM becomes 23:00.
It is the total number of seconds elapsed since 00:00 that day, equal to hours times 3600 plus minutes times 60.
Also known as
TG we-Calculate Editorial Team. (2026). 12-Hour to 24-Hour Time Converter [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/12-hour-to-24-hour-time-converter
TG we-Calculate Editorial Team. "12-Hour to 24-Hour Time Converter." TG we-Calculate. 2026. https://we-calculate.com/calculator/12-hour-to-24-hour-time-converter.
TG we-Calculate Editorial Team, "12-Hour to 24-Hour Time Converter," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/12-hour-to-24-hour-time-converter
@misc{wecalculate_12_hour_to_24_hour_time_converter, title = {12-Hour to 24-Hour Time Converter}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/12-hour-to-24-hour-time-converter}}, year = {2026}, note = {TG we-Calculate} }
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