Add, subtract and convert hours, minutes and seconds. How much time is there between two times or dates?
Enter as many time values as you need. Minutes and seconds above 59 are carried over automatically.
Total time
0:00:00
Enter your time values and press Calculate.
Tip: to subtract a 45-minute lunch break, set a row to − and enter 45 in the minutes box.
Measure elapsed time. Leave the dates blank to compare two clock times on the same day. Overnight spans are detected automatically.
Duration
8:30:00
8 hours and 30 minutes
Start from any date and time, then move forward or backward by weeks, days, hours, minutes and seconds.
Resulting date and time
–
Set a starting point and an amount of time to shift by.
Turn any amount of time into every other unit at once, including the decimal hours that payroll systems expect.
Equivalent time
1:30:00
90 minutes is 1 hour and 30 minutes
Decimal hours are what timesheets, invoices and payroll software use: 7:45 becomes 7.75.
Add and subtract hours, minutes and seconds, measure the duration between two dates or times, shift a date forward or backward, and convert time to decimal hours, all in one tool, with the working shown.
A time calculator adds, subtracts and converts values expressed in hours, minutes and seconds. Time is sexagesimal: seconds and minutes roll over at 60, not at 10, so a standard calculator gets it wrong. Entering 2.45 + 2.45 on a pocket calculator returns 4.90, but 2 h 45 min plus 2 h 45 min is 5 h 30 min. A time calculator performs the base-60 carry for you.
Time arithmetic looks simple until you try it. Most of us learned to count in base 10, where every column carries at ten. Clocks inherited a base-60 (sexagesimal) system from Babylonian astronomers roughly four thousand years ago, and that system never went away. The result is a number format where the columns carry at 60, 60 and 24 in sequence, and where mental arithmetic reliably goes wrong under any kind of time pressure.
This page gives you four calculators that handle those carries automatically:
Everything runs locally in your browser. There is no server call, no account, and no record of what you calculate.
Four steps, about thirty seconds. The calculator updates as soon as you press Calculate, and every mode can show its working.
Use Add & Subtract Time for durations, Time Between for a gap between two moments, Date & Time Math to shift a date, and Convert Units to change format.
Type hours, minutes and seconds into each row. Blank boxes count as zero, and you can enter values over 59, so 0:90:00 is accepted and normalised to 1 h 30 min.
Choose ＋ to add a duration or − to subtract it. Mix both freely: add three work blocks and subtract a lunch break in a single calculation.
You get the answer in HH:MM:SS plus total hours, total minutes, total seconds and decimal hours. Open Show the working to see each carry.
Negative results are fine. If subtractions exceed additions the calculator returns a negative duration, shown with a leading minus sign. That is useful when you are checking whether you are over or under a budgeted number of hours.
Every mode on this page reduces to one idea: convert everything to seconds, do ordinary arithmetic, then convert back.
Any time value collapses into a single integer. This removes the base-60 problem entirely, because integers add and subtract the way we expect.
total_seconds = (hours × 3600) + (minutes × 60) + seconds
So 3:45:20 becomes (3 × 3600) + (45 × 60) + 20 = 10,800 + 2,700 + 20 = 13,520 seconds.
Add or subtract the integers. Ten values or two, it makes no difference.
result = Σ (sign_i × total_seconds_i)
Integer division and remainder rebuild the hours, minutes and seconds. This is where the carrying happens, and doing it in this order guarantees each field lands in range.
hours = floor(result ÷ 3600) minutes = floor((result mod 3600) ÷ 60) seconds = result mod 60
Watch the borrow when subtracting. To compute 3:15 − 1:40 you cannot take 40 from 15. Borrow an hour: 3:15 becomes 2 h 75 min. Then 75 − 40 = 35 and 2 − 1 = 1, giving 1:35. The calculator does this by working in seconds, which sidesteps borrowing entirely.
Exact factors, no rounding. Bookmark or print this section, because it answers most of the conversions people open a time calculator for in the first place.
| Unit | Seconds | Minutes | Hours | Days | Weeks |
|---|---|---|---|---|---|
| 1 second | 1 | 0.016667 | 0.000278 | 0.0000116 | 0.00000165 |
| 1 minute | 60 | 1 | 0.016667 | 0.000694 | 0.0000992 |
| 1 hour | 3,600 | 60 | 1 | 0.041667 | 0.005952 |
| 1 day | 86,400 | 1,440 | 24 | 1 | 0.142857 |
| 1 week | 604,800 | 10,080 | 168 | 7 | 1 |
| 1 month avg | 2,629,746 | 43,829.1 | 730.5 | 30.4375 | 4.3482 |
| 1 year 365 d | 31,536,000 | 525,600 | 8,760 | 365 | 52.1429 |
| 1 leap year | 31,622,400 | 527,040 | 8,784 | 366 | 52.2857 |
Month and year figures use the Gregorian average of 365.2425 days per year. Individual months range from 28 to 31 days, so use the Time Between mode when the exact calendar dates matter.
| Duration | Minutes | Hours | Decimal |
|---|---|---|---|
| 15 minutes | 15 | 0:15 | 0.25 |
| 30 minutes | 30 | 0:30 | 0.50 |
| 45 minutes | 45 | 0:45 | 0.75 |
| 90 minutes | 90 | 1:30 | 1.50 |
| 2 hours | 120 | 2:00 | 2.00 |
| Half shift | 240 | 4:00 | 4.00 |
| Standard shift | 480 | 8:00 | 8.00 |
| Shift minus 30 min lunch | 450 | 7:30 | 7.50 |
| Shift minus 45 min lunch | 435 | 7:15 | 7.25 |
| 12-hour shift | 720 | 12:00 | 12.00 |
| Full day | 1,440 | 24:00 | 24.00 |
| Work week (5 × 8 h) | 2,400 | 40:00 | 40.00 |
| Hours | Minutes | Seconds | Days |
|---|---|---|---|
| 1 hour | 60 | 3,600 | 0.0417 |
| 2 hours | 120 | 7,200 | 0.0833 |
| 4 hours | 240 | 14,400 | 0.1667 |
| 6 hours | 360 | 21,600 | 0.2500 |
| 8 hours | 480 | 28,800 | 0.3333 |
| 10 hours | 600 | 36,000 | 0.4167 |
| 12 hours | 720 | 43,200 | 0.5000 |
| 18 hours | 1,080 | 64,800 | 0.7500 |
| 24 hours | 1,440 | 86,400 | 1.0000 |
| 36 hours | 2,160 | 129,600 | 1.5000 |
| 48 hours | 2,880 | 172,800 | 2.0000 |
| 168 hours | 10,080 | 604,800 | 7.0000 |
This single conversion causes more payroll errors than anything else in time tracking. Seven hours and thirty minutes is 7.5 hours, not 7.30.
Divide the minutes by 60 to get decimal hours; multiply the decimal by 60 to get minutes back.
decimal hours = hours + (minutes ÷ 60) → 7 h 45 min = 7 + (45 ÷ 60) = 7.75 minutes = (decimal − whole) × 60 → 6.4 h = 0.4 × 60 = 24 min → 6 h 24 min| Minutes | Decimal | Minutes | Decimal | Minutes | Decimal | Minutes | Decimal |
|---|---|---|---|---|---|---|---|
| 1 | 0.017 | 16 | 0.267 | 31 | 0.517 | 46 | 0.767 |
| 5 | 0.083 | 20 | 0.333 | 35 | 0.583 | 50 | 0.833 |
| 10 | 0.167 | 25 | 0.417 | 40 | 0.667 | 55 | 0.917 |
| 15 | 0.25 | 30 | 0.50 | 45 | 0.75 | 60 | 1.00 |
| 2 | 0.033 | 17 | 0.283 | 32 | 0.533 | 47 | 0.783 |
| 6 | 0.100 | 21 | 0.350 | 36 | 0.600 | 51 | 0.850 |
| 12 | 0.200 | 24 | 0.400 | 42 | 0.700 | 54 | 0.900 |
| 18 | 0.300 | 27 | 0.450 | 48 | 0.800 | 57 | 0.950 |
Bold rows are the quarter-hour marks. Many employers round clock punches to the nearest quarter hour; in the United States this is permitted under the Fair Labor Standards Act only when the rounding is neutral over time and does not systematically favour the employer.
Wages are a multiplication: hours × rate. You cannot multiply 7:45 by $28.50 directly, but 7.75 × 28.50 = $220.88 works in any spreadsheet. Decimal hours make time compatible with money.
Writing 7 h 30 min as 7.30 understates the shift by 12 minutes across a five-day week. Over a year that is roughly 52 hours of unpaid or unbilled work. Always divide by 60.
Keep three decimal places when summing a week, and round only the final total. Rounding each day first can drift by several minutes by Friday.
Five ways of seeing the same structure: how the units nest, how a day divides, how an overnight span is measured, and how minutes map onto decimals.
Each one is solvable in the calculator above. The working is shown so you can check your own method against it.
You clock in at 8:30 AM, clock out at 5:15 PM, and take a 45-minute unpaid lunch. How many hours do you bill?
= 8:00:00 → 8.00 paid hours
Dinner is served at 6:30 PM. The roast needs 3 h 20 min in the oven and 25 min resting afterwards.
= 14:45 → put it in at 2:45 PM
Your four laps were 1:32, 1:29, 1:35 and 1:28. What is the total, and the average?
Total 6:04 · Average 1:31 per lap
You quoted 10 hours. So far you have logged 2:45, 1:20, 0:50 and 3:15. How much budget is left?
Used 8:10 · Remaining 1:50 (1.83 h)
You leave Toronto on Friday at 9:45 PM. The flight is 7 h 35 min and London is 5 hours ahead in July.
Lands 10:20 AM Saturday, London time
You start at 10:00 PM and finish at 6:15 AM with a 30-minute unpaid break.
= 7:45:00 → 7.75 paid hours
The same moment can be written half a dozen ways. Mixing formats mid-calculation is one of the most common sources of error.
| Format | Example | Range | Where you meet it |
|---|---|---|---|
| 12-hour clock | 3:30 PM | 1 to 12 with AM/PM | Everyday speech and writing in the US, Canada, UK, Australia and the Philippines. |
| 24-hour clock military | 15:30 · 1530 | 00:00 to 23:59 | Most of the world, plus aviation, healthcare, transport and the military everywhere. |
| Decimal hours | 15.5 h | Any real number | Payroll, invoicing, timesheets, spreadsheets. Required whenever time is multiplied by a rate. |
| Duration HH:MM:SS | 15:30:00 | Unbounded | Stopwatches, video editing, race results. Hours can exceed 24 because it measures length, not a moment. |
| ISO 8601 duration | PT15H30M | Unbounded | APIs, calendar files, structured data. P for period, T for time, then each unit with its letter. |
| Total seconds | 55,800 | Integer | Databases, log files, Unix timestamps, and every calculation on this page internally. |
12:00 AM → 00:00 (midnight is zero, not twelve) 1:00 AM to 11:59 AM → keep the hour, pad to two digits 12:00 PM → 12:00 (noon stays twelve) 1:00 PM to 11:59 PM → add 12 to the hour
The two edge cases at midnight and noon catch almost everyone. 12:30 AM is 00:30, half past midnight and very early in the day. 12:30 PM is 12:30, half past noon. Going the other way, any 24-hour value of 13:00 or higher becomes PM after subtracting 12.
| 12-hour | 24-hour | 12-hour | 24-hour |
|---|---|---|---|
| 12:00 AM | 00:00 | 12:00 PM | 12:00 |
| 1:00 AM | 01:00 | 1:00 PM | 13:00 |
| 2:00 AM | 02:00 | 2:00 PM | 14:00 |
| 4:00 AM | 04:00 | 4:00 PM | 16:00 |
| 6:00 AM | 06:00 | 6:00 PM | 18:00 |
| 8:00 AM | 08:00 | 8:00 PM | 20:00 |
| 10:00 AM | 10:00 | 10:00 PM | 22:00 |
| 11:59 AM | 11:59 | 11:59 PM | 23:59 |
Different jobs, one recurring problem: base-60 arithmetic that has to be right the first time.
Totalling punches, removing unpaid breaks, splitting regular from overtime hours, and converting to the decimal format the payroll system will accept.
Adding time entries across a week, checking logged hours against a fixed quote, and turning HH:MM into billable decimal hours for the invoice.
Overnight shifts that cross midnight, rotating rosters, handover overlaps, and medication schedules counted in hours from the last dose.
Summing splits, computing average lap or kilometre pace, comparing this week's session total against last week's.
Working backwards from a serving time through resting, proofing, cooking and prep so everything lands together.
Rolling task estimates into a phase total, checking a critical path against a deadline, and reporting effort in consistent units.
Adding clip durations, finding the runtime gap to a target length, and converting timecode positions into total seconds.
Elapsed-time homework, revision schedules, exam timing, and checking answers on base-60 arithmetic problems.
Flight durations across time zones, layover windows, and whether a connection is actually long enough to make.
Almost every incorrect time answer traces back to one of these.
| Mistake | What it looks like | The fix |
|---|---|---|
| Treating minutes as decimals | 7:30 written as 7.30 | Divide minutes by 60. 7:30 is 7.50. The error is 12 minutes per shift. |
| Forgetting the midnight wrap | 22:00 → 06:00 = −16 h | Add 24 hours to the end time when it falls before the start. The answer is 8 h. |
| Mixing 12- and 24-hour values | Subtracting 5:00 PM as 5:00 | Convert everything to one format first. 5:00 PM is 17:00. |
| Not carrying past 59 | 36 h 135 min left as-is | 135 minutes is 2 h 15 min. The total becomes 38 h 15 min. |
| Rounding too early | Rounding each day, then summing | Keep full precision through the week and round only the final figure. |
| Assuming every day is 24 hours | DST changeover days | Days when clocks shift run 23 or 25 hours. Check the calendar date, not just the clock. |
There is more than one way to add up hours. Here is where each approach holds up and where it breaks.
| Method | Handles base-60 carries | Crosses midnight | Gives decimal hours | Shows working | Speed |
|---|---|---|---|---|---|
| Mental arithmetic | Sometimes, but error-prone past two values | Manual | No | In your head | Fast but unreliable |
| Pocket calculator | No. Base 10 only | No | Only if you pre-convert | No | Fast, frequently wrong |
| Spreadsheet formula | Yes with correct cell formatting | Needs a conditional | Yes with *24 | No | Slow to set up, fast after |
| Phone stopwatch | Live only | Yes | No | No | Only for live timing |
| This time calculator recommended | Yes, automatically | Yes, detected | Yes, always shown | Yes, step by step | Instant |
Spreadsheet note: format the result cell as [h]:mm rather than h:mm, otherwise totals above 24 hours silently wrap back to zero, a classic source of understated timesheets.
The vocabulary you will meet in timesheets, schedules and technical documentation.
36:00:00 is valid as a duration but never as a clock reading.PT2H30M for two and a half hours. Used in APIs, calendar files and structured data.Direct answers to what people most often ask about calculating time.
A time calculator is a tool that performs arithmetic on time values expressed in hours, minutes and seconds. Because time uses a base-60 system rather than base-10, ordinary calculators give wrong answers: 2:45 plus 2:45 is 5:30, not 5.90. A time calculator carries every 60 seconds into a minute and every 60 minutes into an hour automatically, so the result is always correct.
Add the seconds columns first, then the minutes, then the hours. If the seconds total 60 or more, subtract 60 and carry 1 to the minutes. If the minutes total 60 or more, subtract 60 and carry 1 to the hours.
For example, 3 h 45 min plus 2 h 30 min gives 75 minutes, which becomes 1 hour and 15 minutes, so the answer is 6 h 15 min.
Convert both times to seconds since midnight, subtract the earlier from the later, then convert back to hours, minutes and seconds. If the end time is earlier than the start time the period crosses midnight, so add 24 hours (86,400 seconds) to the end time before subtracting.
From 9:15 AM to 5:45 PM is 8 hours 30 minutes.
Divide the minutes by 60. For example 45 minutes ÷ 60 = 0.75, so 7 hours 45 minutes is 7.75 decimal hours. To go the other way, multiply the decimal part by 60: 6.4 hours means 0.4 × 60 = 24 minutes, giving 6 hours 24 minutes.
Payroll and timesheet systems almost always expect decimal hours, because wages are calculated by multiplying hours by an hourly rate.
A standard calculator works in base 10, where each column rolls over at 10. Time is sexagesimal: seconds and minutes roll over at 60 and hours roll over at 24. Typing 1.45 + 1.45 into a normal calculator returns 2.90, but 1 h 45 min plus 1 h 45 min is 3 h 30 min. The two only agree if you first convert the minutes to decimal hours.
There are 86,400 seconds in a standard 24-hour day: 24 × 60 × 60. A day is 1,440 minutes. A week is 604,800 seconds, and a common 365-day year is 31,536,000 seconds. Days on which daylight saving time starts or ends run 23 or 25 hours instead.
Work out the total span from clock-in to clock-out, then subtract the unpaid break as a separate time value. A shift from 8:30 AM to 5:00 PM is 8 hours 30 minutes; taking off a 45-minute lunch leaves 7 hours 45 minutes, which is 7.75 decimal hours for payroll.
The Time Between mode has a dedicated break field that does this in one step.
Yes. In the Time Between mode, if the end time falls before the start time on the same day the calculator adds a full 24 hours automatically, so a 10:00 PM to 6:00 AM overnight shift returns 8 hours. Filling in the date fields removes any ambiguity for shifts longer than 24 hours.
Military time, also called 24-hour time, counts hours from 00 to 23 with no AM or PM. For PM times from 1:00 PM onward, add 12 to the hour: 3:30 PM becomes 15:30. For AM times, keep the hour and pad it to two digits: 7:05 AM becomes 07:05. Midnight is 00:00 and noon is 12:00.
It is completely free, requires no account, and every calculation runs locally in your browser using JavaScript. Nothing you type is transmitted to a server or stored anywhere, and once the page has loaded it keeps working without an internet connection.
The calculator works to the second and correctly handles leap years and varying month lengths, because it compares two real timestamps rather than estimating. It does not adjust for daylight saving transitions or time zone changes, so a span that crosses a DST boundary in your region may differ by one hour from wall-clock time.
Split the 90 minutes into 1 hour and 30 minutes, then add each part. Adding 90 minutes to 2:20 PM gives 3:50 PM. In the Date & Time Math mode you can type 90 straight into the minutes box and the calculator carries the hour for you, rolling over to the next day if needed.
In everyday use they mean the same thing: the amount of time between a start point and an end point. Elapsed time usually implies you measured it against a clock that was running, such as a stopwatch or a shift. Duration describes the length of an interval in the abstract, such as a 90-minute meeting.
Add every lap time together with the time calculator to get a total, then divide that total by the number of laps. Four laps of 1:32, 1:29, 1:35 and 1:28 total 6:04, which is 364 seconds; dividing by 4 gives 91 seconds, or an average lap of 1:31.