Add or subtract hours, minutes, and seconds, find the elapsed time between two clock times, calculate a time before or after another clock time, and convert between 12-hour and 24-hour time.
Choose a mode below, enter your values, and press Calculate.
Time arithmetic looks like ordinary addition and subtraction, but it uses different unit boundaries. Sixty seconds make one minute. Sixty minutes make one hour. That means 45 minutes plus 30 minutes does not stay "75 minutes" after normalization. Seventy-five minutes becomes 1 hour, 15 minutes. A time calculator handles that carrying and borrowing automatically.
Seconds, minutes, and hours do not use base-10 boundaries. Sixty seconds make a minute, sixty minutes make an hour, and 24 clock hours make a day.
| Unit Group | Equals |
|---|---|
| 60 seconds | 1 minute |
| 60 minutes | 1 hour |
| 24 clock hours | 1 day |
Suppose you want to add 2 hours, 45 minutes, 30 seconds and 1 hour, 30 minutes, 45 seconds. One reliable method is to convert both durations to seconds first.
45 plus 30 is 75 minutes, which carries into 1 hour, 15 minutes. That carry is why 2:45 plus 1:30 becomes 4:15, not "3:75."
| Step | Value |
|---|---|
| 2:45 + 1:30, minutes only | 45 + 30 = 75 minutes |
| 75 minutes normalized | 1 hour, 15 minutes |
| Result | 4:15 |
Subtraction works the same way. Convert each duration to one common unit, subtract, then convert the result back into hours, minutes, and seconds. This avoids the confusing process of borrowing 60 seconds from one minute, or 60 minutes from one hour, by hand.
Suppose the start is 8:01 AM and the end is 8:13 AM. The elapsed time is 12 minutes. For longer spans, converting each clock time into minutes (or seconds) after midnight makes the subtraction easier. For example, 9:15 AM equals (9 × 60) + 15 = 555 minutes after midnight, and 5:45 PM is 17:45, which equals (17 × 60) + 45 = 1,065 minutes. The difference is 1,065 minus 555 = 510 minutes, which is 8 hours, 30 minutes.
A clock resets after midnight, so 10:00 PM to 6:00 AM looks backward if you compare the clock numbers directly. Instead, convert both to minutes after midnight: 10 PM is 22:00, which is 22 × 60 = 1,320 minutes after midnight. 6 AM the next day is 360 minutes, and adding one day gives 360 + 1,440 = 1,800. The difference is 1,800 minus 1,320 = 480 minutes, which is 8 hours.
10 PM to midnight to 6 AM is 8 hours total, even though "6" is a smaller number than "10." The calculator above makes the same-day/next-day assumption visible instead of guessing.
| Segment | Length |
|---|---|
| 10 PM to midnight | 2 hours |
| Midnight to 6 AM | 6 hours |
| Total | 8 hours |
This is a different type of time calculation: start with a clock time and add a duration. For example, 10:30 PM plus 5 hours 45 minutes: 10:30 PM plus 1 hour 30 minutes reaches midnight, and 4 hours 15 minutes remain, for a result of 4:15 AM the next day. The Time Calculator says "Next day" without inventing a calendar date. If you need the actual date too, use the Date Calculator.
Subtraction works in reverse. For example, 3:00 AM minus 5 hours passes midnight backward, for a result of 10:00 PM the previous day. Again, this page handles the clock rollover. The Date Calculator handles actual calendar-date movement.
Clock time describes a position on a daily clock, such as 8:00 AM, 2:30 PM, or 23:15. Duration describes an amount of elapsed time, such as 3 hours, 45 minutes, or 90 seconds. A duration can be longer than 24 hours. A clock time repeats every day. That distinction matters: a duration of 26 hours should remain 26 hours, while a clock time advanced by 26 hours wraps one full day plus another two hours.
A 26-hour duration stays 26 hours. A clock time moved forward by 26 hours wraps to the next day, plus 2 more hours.
| Type | 26-Hour Result |
|---|---|
| Duration | Stays 26 hours; not wrapped |
| Clock time | Wraps to next day, plus 2 hours |
Modern clock arithmetic groups 60 seconds into a minute and 60 minutes into an hour. NIST recognizes the minute and hour as time units accepted for use with the SI, and defines their relationship to the second: 1 minute equals 60 seconds, 1 hour equals 60 minutes (3,600 seconds), and 1 day equals 24 hours (86,400 seconds). The BIPM defines the second as the SI base unit of time. For ordinary calculator users, the practical lesson is simply that seconds, minutes, and hours do not use base-10 boundaries.
No, and this is a common error. 1 hour 30 minutes equals 1 + 30/60 = 1.5 decimal hours. So 1:30 as a clock-style duration equals 1.50 decimal hours, not 1.30. The Minute Calculator handles detailed minute-to-decimal conversions for timesheets and payroll.
The 12-hour clock uses AM and PM. The 24-hour clock runs from 00:00 through 23:59. For example, 1:00 PM equals 13:00, 6:30 PM equals 18:30, and 11:45 PM equals 23:45. Midnight, written 12:00 AM, equals 00:00. Noon, written 12:00 PM, equals 12:00.
Noon and midnight are the two values people most often convert incorrectly, since both use "12" in the 12-hour clock.
| 12-Hour Time | 24-Hour Time |
|---|---|
| 1 PM | 13:00 |
| 11 PM | 23:00 |
| 12 AM (midnight) | 00:00 |
| 12 PM (noon) | 12:00 |
In everyday U.S. usage, "military time" usually refers to the 24-hour clock format. A military-style display may omit the colon in some contexts, such as 1730 for 5:30 PM. The underlying hour conversion is still the same as any 12-hour-to-24-hour conversion.
Use the Time Calculator for adding durations, subtracting durations, finding elapsed clock time, finding a time before or after a clock time, and 12-hour/24-hour conversion. Use the Hours Calculator for work shifts, clock-in and clock-out totals, lunch breaks, weekly hours, overtime estimates, and hourly pay. Use the Minute Calculator for minutes between times, minutes-to-decimal-hours conversion, decimal-hours-to-minutes conversion, and payroll rounding examples.
Time math is easiest when everything is converted into one consistent unit first. Seconds are especially useful because one minute equals 60 seconds and one hour equals 3,600 seconds. CalculateThisWay performs the carrying, borrowing, midnight rollover, and format conversion automatically, while still showing enough of the math for you to understand the answer.
The answers below are computed live by the same engine as the calculator above, so they will always match what entering these exact values into the calculator would return.
2 h 45 m 30 s + 1 h 30 m 45 s
9,930 seconds + 5,445 seconds = 15,375 seconds
2 h 45 m 30 s - 1 h 30 m 45 s
9,930 seconds - 5,445 seconds = 4,485 seconds
Start 8:01 AM, End 8:13 AM, same day
Start 10:00 PM, End 6:00 AM next day
10:30 PM + 5 h 45 m
13:30 in 12-hour time
Duration 1: 2 h 45 m 30 s. Operation: Add. Duration 2: 1 h 30 m 45 s.
What is the total, and why doesn't 45 + 30 stay "75 minutes" in the final answer?
The total is 4 hours, 16 minutes, 15 seconds. The 45 seconds plus 45 seconds (30 + 45 before normalizing) and the carried minutes get regrouped into whole hours and minutes, the same way carrying works in ordinary addition, just with a base of 60 instead of a base of 10.
I want to add or subtract clock durations, find time between two clock times, or convert 12-hour and 24-hour time.
I want a future or past calendar date, or the number of days between two dates.
I want a countdown to an event, or how many calendar days since, until, or between dates.
I want a full work shift, weekly total, overtime, or gross pay.
I want minutes between two times, decimal-hour conversion, or payroll rounding.
Convert each duration into seconds (hours times 3,600, plus minutes times 60, plus seconds), add the two totals together, then convert the sum back into hours, minutes, and seconds.
Convert both durations into seconds, subtract the second total from the first, then convert the result back into hours, minutes, and seconds.
Enter the hours and minutes for each duration in the Add or Subtract Durations mode above. Seconds are optional and default to zero.
Use the Time Between Two Clock Times mode above. Enter a start time and an end time, and the calculator finds the elapsed duration between them.
Convert both clock times to seconds after midnight and subtract the earlier one from the later one. The calculator above does this automatically and also handles a span that crosses midnight.
8:01 AM to 8:13 AM is 12 minutes.
9:00 AM to 5:00 PM is 8 hours.
Add 24 hours (86,400 seconds) to the end time before subtracting, or choose the End Time Is: Next day option in the calculator above so the calculator knows the end time crossed midnight.
Add 8 hours to the current clock time using the Add or Subtract Time From a Clock mode above. The result notes whether it lands on the same day or the next day.
Use the same Add or Subtract Time From a Clock mode, set Operation to Subtract, and enter 5 hours.
No. 1:30 as a clock-style duration (1 hour 30 minutes) equals 1.50 decimal hours, not 1.30. This is a common error.
Divide the number of minutes by 60. For example, 90 minutes divided by 60 equals 1.5 hours.
90 minutes equals 1.5 hours, or 1 hour and 30 minutes.
60 seconds make one minute.
3,600 seconds make one hour (60 seconds times 60 minutes).
60 minutes make one hour.
Use the Convert 12-Hour / 24-Hour Time mode above. For PM times, add 12 to the hour (except 12 PM itself, which stays 12:00). 12 AM becomes 00:00.
1 PM is 13:00 in 24-hour time.
Midnight (12:00 AM) is 00:00 in military time.
Noon (12:00 PM) is 12:00 in military time.
Yes. A duration such as 26 hours stays 26 hours and is not wrapped back to zero, because a duration is an amount of elapsed time rather than a position on a daily clock.
A clock repeats every 24 hours, so adding a duration to a clock time rolls over into the next day, or a later day, once the total passes midnight.
No. This calculator handles clock and duration math only. For actual calendar dates, use the Date Calculator or Day Counter.
No. For work-shift hours, clock-in and clock-out totals, or pay calculations, use the Hours Calculator or Minute Calculator.
Use the Hours Calculator for work shifts, clock-in and clock-out times, breaks, weekly totals, and overtime estimates.
Use the Minute Calculator for minutes-to-decimal conversions and payroll rounding examples.