How to use the time calculator
- Add or subtract durations — two lengths of time in days, hours, minutes and seconds, joined by + or −. Minutes and seconds above 59 are fine (90 minutes is simply 1:30:00); the calculator carries for you.
- Time between two clock times — a start and an end time. An end earlier than the start is taken as the next day; tick the box to force "next day" when the end is later, e.g. 09:00 to 09:00 for a full 24 hours.
- Add a duration to a clock time — a time of day plus or minus hours and minutes. You get the clock time and whether it lands on the same, the next or the previous day.
How time arithmetic works
Clock arithmetic is base 60 for seconds and minutes and base 24 for hours, which is where hand calculations go wrong. The calculator avoids carrying: convert everything to seconds, do ordinary arithmetic, convert back.
- To seconds: days × 86,400 + hours × 3,600 + minutes × 60 + seconds.
- Back to h:mm:ss: divide by 3,600 for hours; the remainder divided by 60 gives minutes; what is left is seconds. Every 86,400 seconds is a day.
- Decimal hours = total seconds ÷ 3,600. Note that 2:30 is 2.5 hours, not 2.3 — minutes are divided by 60, not moved behind a decimal point.
By hand, work column by column: add the seconds and carry 60 as one minute, then the minutes and carry 60 as one hour. Subtraction borrows the same way: 3:10 − 1:45 becomes 2:70 − 1:45 = 1:25.
Worked example: a week of hours for payroll
A part-time employee worked 7:45, 6:20, 8:05, 7:50 and 4:30 over five days. The minutes add to 45 + 20 + 5 + 50 + 30 = 150, which is 2 hours 30 minutes; the hours add to 32. Total: 34:30, or 34.5 hours. At $18 per hour the gross pay is 34.5 × 18 = $621.00; read as "34.30 hours" it would come out $3.60 short every pay period, which is why payroll works in decimal hours. For a shift with an unpaid break, the hours calculator subtracts the break; the time card calculator totals a week of in and out times.
Hours and minutes to decimal hours
| h:mm | Decimal hours |
|---|---|
| 0:15 | 0.25 |
| 0:30 | 0.50 |
| 0:45 | 0.75 |
| 1:00 | 1.00 |
| 1:15 | 1.25 |
| 1:30 | 1.50 |
| 1:45 | 1.75 |
| 2:00 | 2.00 |
Minutes alone, for any number of hours:
| Minutes | Decimal (2 places) | Exact |
|---|---|---|
| 5 | 0.08 | 0.0833 |
| 10 | 0.17 | 0.1667 |
| 15 | 0.25 | 0.2500 |
| 20 | 0.33 | 0.3333 |
| 25 | 0.42 | 0.4167 |
| 30 | 0.50 | 0.5000 |
| 35 | 0.58 | 0.5833 |
| 40 | 0.67 | 0.6667 |
| 45 | 0.75 | 0.7500 |
| 50 | 0.83 | 0.8333 |
| 55 | 0.92 | 0.9167 |
| 60 | 1.00 | 1.0000 |
Many payroll systems round to the nearest quarter hour (0.25) or tenth of an hour (6 minutes); under US federal rules the rounding must not work only in the employer's favor — check your handbook.
Crossing midnight
A shift from 22:00 to 06:00 looks negative if you subtract directly: 6 − 22 = −16 hours. The calculator adds 24 hours (1,440 minutes) whenever the end time is earlier than the start, giving 8 hours. The same correction applies when adding a duration: 23:30 plus 2 hours is 25:30, which is 01:30 the next day. Times in different zones should be converted first with the time zone converter; for spans between dates, use the days between dates calculator.
Time calculator or hours calculator?
Use this page for durations themselves — adding segments, the gap between two times, a finish time. The hours calculator is built for one work shift: start and end time, minus an unpaid break, times an hourly rate. If your question has a lunch break or a paycheck in it, start there.
Frequently asked questions
How do I add hours and minutes?
Add the minutes first; every 60 minutes becomes one hour carried into the hours column. 2:45 + 1:30: 45 + 30 = 75 minutes = 1 hour 15 minutes, so the total is 2 + 1 + 1 = 4 hours 15 minutes, or 4.25 hours.
How do I convert minutes to decimal hours?
Divide the minutes by 60: 20 minutes is 0.33 hours, 45 minutes is 0.75 and 50 minutes is 0.83. The other way, multiply the decimal part by 60: 0.4 hours is 24 minutes.
How many hours is it from 10 PM to 6 AM?
Eight hours. Because 06:00 is earlier on the clock than 22:00, the end time is on the next day: 6 + 24 − 22 = 8.
What time will it be in 90 minutes?
Choose "Add a duration to a clock time", enter the current time and 1 hour 30 minutes (or 90 minutes — both work). The result gives the clock time and says whether it falls on the next day.
Why does the result show a minus sign?
In the add/subtract mode the second duration was longer than the first, so the difference is negative — 1:15:00 − 2:00:00 = −0:45:00. Swap the two durations if you only want the size of the gap.
Last updated: October 9, 2026