Timer Calculator
A free timer calculator that adds or subtracts hours, minutes, and seconds or finds a timer's end time, with no sign-up and on your phone.
Timer calculator
Blank boxes count as 0. Minutes and seconds over 59 carry over for you.
Total
Result is negative.
- As hours:minutes:seconds
- 0:00:00
- Decimal hours
- 0.00
- Total minutes
- 0
- Total × 1
Quick picks
Ends at
· 24-hour --
Timer
Stop the timer? It still has time left.
More time tools
- Hours ago and from nowWhat time was it 8 hours ago, with a 1 to 24 hour table.
- Time durationHours and minutes between two times or two dates.
- Elapsed timeTime between two clock times, with the steps shown.
- Military time converter1700 to 5:00 PM and back, plus a full chart.
- Time unit converterMinutes to hours, seconds to minutes, and back, with hours and minutes shown.
- How long until 5 PMHours, minutes, and seconds from now until any time.
- Online timerA countdown with an alarm and full-screen view.
- Interval timerTabata, HIIT and EMOM workouts with phase beeps.
- Focus timerFocus sessions and breaks, one after another.
- Classroom timerA shrinking disk and named activities for the projector.
- Online alarm clockRing at a time of day instead of after a set length.
- StopwatchLaps, notes, and a CSV download of your times.
Need a fixed length? Start a 1 minute, 5 minute or 10 minute timer in one tap.
How adding time works
| When a column reaches | Carry |
|---|---|
| 60 seconds | 1 minute |
| 60 minutes | 1 hour |
| 24 hours | 1 day on a clock. Totals here keep counting hours, so 28 hours stays 28 h. |
Time is counted in base 60. There are 60 seconds in a minute and 60 minutes in an hour, so when a column passes 59 you carry 1 to the next column, the same way you carry 1 at 10 in ordinary addition.
80 seconds is 1 minute 20 seconds. 66 minutes is 1 hour 6 minutes. The calculator turns every row into seconds, adds them, and turns the total back into hours, minutes, and seconds, so nothing gets lost in the carrying.
Clock times work a little differently. A clock rolls over at midnight, so adding 7 hours 30 minutes to 10:30 PM lands on the next morning. The What time will it be tab tracks the date for you and says whether the answer is today, tomorrow, or yesterday.
If you want to do it on paper, the guide to adding and subtracting time by hand walks through carrying, borrowing, and negative results. More worked examples are in the guides to time math and telling time.
Two sums worked by hand
Adding two durations
2 h 40 min 30 s + 1 h 25 min 50 s:
- Seconds: 30 + 50 = 80 s, which is 1 min 20 s. Write 20 s and carry 1 minute.
- Minutes: 40 + 25 + 1 carried = 66 min, which is 1 h 6 min. Write 6 min and carry 1 hour.
- Hours: 2 + 1 + 1 carried = 4 h.
Total: 4 h 6 min 20 s, or 4.11 decimal hours.
Finding an end time past midnight
10:30 PM + 7 h 30 min. In 24-hour time that is 22:30 + 7:30 = 30:00. Take away 24 hours for the new day and you get 6:00, so the answer is 6:00 AM tomorrow.
Timer calculator questions
How do I add hours and minutes?
Add the seconds first, then the minutes, then the hours. Every time seconds reach 60, carry 1 minute. Every time minutes reach 60, carry 1 hour. For example, 40 min + 25 min = 65 min, which is 1 h 5 min. The calculator does this for every row and can show each carrying step.
How do I subtract time?
Switch a row to minus. The calculator turns every row into seconds, adds or subtracts them, then turns the total back into hours, minutes, and seconds. If the total is negative, it shows a minus sign and tells you.
What time will it be in 8 hours?
Open the What time will it be tab, leave Start from on Now, and tap the 8 h quick pick. The answer uses your device clock. For a full list of 1 to 24 hours ago and from now, use the hours ago calculator.
Can I start a timer for the result?
Yes. When the end time is in the future, the Start this timer button runs a countdown to that exact moment. It counts against the clock rather than counting ticks, so it stays correct if you switch tabs. Sound plays only after you have clicked the page, because browsers block sound until then.
Does it use my time zone?
Yes. Clock answers come from your device's clock and time zone, which are shown next to the result and in the side panel. If your device clock is wrong, the answer will be off by the same amount.
Why does my spreadsheet show the wrong total after 24 hours?
Spreadsheets often format a time total as a clock, which rolls over at 24 hours, so 28 hours shows as 4:00. In Excel, the custom number format [h]:mm:ss keeps counting past 24. This calculator never rolls a total over, so 52 hours 15 minutes stays 52:15. The Excel time guide covers [h]:mm totals and overnight spans.
Sources
- TeachExcel, "Summing time greater than 24 hours" (the [h]:mm:ss format), teachexcel.com
The Timer Calculator on TimerCalculator.com was built by Cedrick Reese. Every result is worked out in whole seconds, so there's no rounding drift between rows, and decimal hours are rounded to two places only at the end. Before this version went live, both worked examples above were entered into the calculator by an automated browser test, which confirmed 4 h 6 min 20 s for the two durations and 6:00 AM the next day for 10:30 PM plus 7 h 30 min. The same test set the browser to a simulated clock to check the Now option. Clock answers use your own device's time and time zone, so nothing here depends on stored data that could go out of date.