Time Calculator
Add or subtract hours, minutes, and seconds. Calculate duration between two times. Enter values in any combination — the calculator handles overflow and conversion automatically. 100% browser-based.
A time calculator is a free, browser-based tool that adds or subtracts durations in hours, minutes, and seconds, and measures the elapsed time between two clock times. It converts each entry to total seconds, does the arithmetic, and returns the answer in h:m:s, digital HH:MM:SS, total seconds, total minutes, and decimal hours for timesheets. Updated 2026-08-11.
How the Time Calculator Works
This time calculator lets you add or subtract time durations expressed in hours, minutes, and seconds. It converts everything to total seconds internally, performs the arithmetic, then converts back to a readable hours:minutes:seconds format. The calculator handles overflow automatically — for example, 75 minutes becomes 1 hour and 15 minutes.
You can use this for calculating total work hours, adding up exercise durations, figuring out cooking times, computing travel durations, or any situation where you need to add or subtract time values. Enter the first time, choose add or subtract, enter the second time, and get your result instantly.
Time Calculation Method
Total Seconds = (Hours × 3600) + (Minutes × 60) + Seconds
Result = Time 1 Total Seconds ± Time 2 Total Seconds
Hours = floor(Result / 3600), Minutes = floor(Remainder / 60), Seconds = Remainder
Where:
- 3600 = seconds in one hour
- 60 = seconds in one minute
- Negative results are shown with a minus sign
Example Calculations
Example 1: Add Two Work Shifts
Morning shift: 4 hours 30 minutes + Afternoon shift: 3 hours 45 minutes
- Time 1: 4h 30m 0s = 16,200 seconds
- Time 2: 3h 45m 0s = 13,500 seconds
- Total: 29,700 seconds = 8 hours 15 minutes 0 seconds
Example 2: Subtract Break Time
Total shift: 8 hours 0 minutes − Lunch break: 0 hours 45 minutes
- Time 1: 8h 0m 0s = 28,800 seconds
- Time 2: 0h 45m 0s = 2,700 seconds
- Result: 26,100 seconds = 7 hours 15 minutes 0 seconds
Example 3: Add Race Lap Times
Lap 1: 1 minute 32 seconds + Lap 2: 1 minute 28 seconds
- Time 1: 0h 1m 32s = 92 seconds
- Time 2: 0h 1m 28s = 88 seconds
- Total: 180 seconds = 0 hours 3 minutes 0 seconds
Duration Between Two Clock Times (Including Overnight Shifts)
Set the Operation dropdown to Duration between two clock times and the two entries stop being durations and become points on a 24-hour clock. Enter 22 h 30 m as Time 1 and 6 h 15 m as Time 2 and the answer is 7 hours 45 minutes, not a negative number — an end time earlier than the start is read as the next day, which is what an overnight shift actually is. Enter clock times in 24-hour form: 9:15 AM is 9 h 15 m, and 5:30 PM is 17 h 30 m. The result also reports decimal hours (7.75), which is the format US payroll systems expect; the US Department of Labor recordkeeping rules (Fact Sheet 21) require employers to keep the hours worked each day and each workweek, so this is the number that belongs on the timesheet.
Common Uses for Time Calculation
Time calculators are used daily by employees tracking work hours, runners adding lap times, cooks combining recipe preparation and cooking durations, project managers estimating task completion, students calculating study time, and travelers adding flight durations with layovers. Any scenario where you need to combine or compare time durations benefits from a simple time calculator.
Entering PM and Military Time in the Time Calculator
The Time 1 and Time 2 boxes use the 24-hour clock, so an afternoon time has to be entered as its 24-hour value or the answer comes out wrong. The rule is simple: for any PM time except noon, add 12 to the hour. 1 PM is 13, 5 PM is 17, 9:15 PM is 21 h 15 m, and 11:45 PM is 23 h 45 m. Going the other way, 12 AM (midnight) is 0, and 12 PM (noon) stays 12 — those two are the pair people reverse most often. Military and 24-hour notation drop the colon, so "1730" means 17 h 30 m, and "0045" means 0 h 45 m. The United States civil day officially starts at 00:00:00 and runs to 23:59:59, as defined by the NIST Time and Frequency Division. If your shift crosses midnight, enter both times as 24-hour values and switch the Operation dropdown to "Duration between two clock times" — the calculator rolls over to the next day instead of returning a negative. Updated 2026-08-18.
Converting Time to Decimal Hours for Payroll
Payroll systems do not accept 7 hours 45 minutes — they want 7.75. The conversion is one division: take the minutes, divide by 60, and add the result to the hours. So 7h 45m becomes 7 + (45 ÷ 60) = 7.75, 6h 20m becomes 6 + (20 ÷ 60) = 6.33, and 8h 10m becomes 8.17. The mistake that costs real money is writing 7.45 for 7h 45m — that is 7 hours 27 minutes, and repeated across a fortnightly timesheet it quietly removes close to an hour of paid work.
The quick reference for common minute values: 5m = 0.08, 10m = 0.17, 15m = 0.25, 20m = 0.33, 30m = 0.50, 40m = 0.67, 45m = 0.75, 50m = 0.83. Add the duration in this calculator first, then convert the total once at the end rather than converting each shift — converting early and rounding each line is where cumulative error creeps in.
On rounding: US employers may record time in quarter-hour increments, but under 29 CFR § 785.48 the practice is only lawful if it averages out neutrally over time — rounding that consistently favours the employer is not permitted. The common compliant pattern is the 7-minute rule: minutes 1-7 past a quarter round down, minutes 8-14 round up. Keep the exact clock times as well as the rounded figure, since the exact record is what settles a dispute. Updated 2026-08-26.
Time Conversion Reference
For quick reference: 1 hour = 60 minutes = 3,600 seconds. 1 day = 24 hours = 1,440 minutes = 86,400 seconds. 1 week = 168 hours. When the result exceeds 24 hours, this calculator shows the total hours (e.g., 26 hours 15 minutes) rather than converting to days, which is more practical for most use cases.
Frequently Asked Questions
Can I add more than two time values?
This calculator handles two time values at once. To add three or more times, calculate the first two, then use the result as Time 1 and enter the third value as Time 2. Repeat as needed.
What happens if I subtract a larger time from a smaller one?
The result will be negative, shown with a minus sign. For example, 2 hours minus 3 hours gives −1 hour. This is useful for calculating time deficits or overruns.
Can I enter more than 60 minutes or 60 seconds?
Yes. The calculator converts everything to total seconds internally, so entering 90 minutes is the same as entering 1 hour and 30 minutes. It handles all overflow automatically.
What is decimal hours?
Decimal hours express time as a single number with decimals instead of hours:minutes:seconds. For example, 1 hour 30 minutes = 1.5 decimal hours. This format is commonly used in timesheets and payroll systems.
Is this accurate for payroll time tracking?
Yes. The calculator is precise to the second. For payroll, use the decimal hours output which is the standard format for timesheet calculations. Always verify with your company's payroll rounding rules.
How do I calculate the duration between two times?
Set the Operation dropdown to "Duration between two clock times", then enter your start time as Time 1 and your end time as Time 2 using the 24-hour clock — 9:15 AM is 9 hours 15 minutes, and 5:30 PM is 17 hours 30 minutes. The calculator returns the elapsed time in h:m:s, digital HH:MM:SS, and decimal hours.
How do I enter a PM time in the time calculator?
Add 12 to the hour for any PM time except noon. 1 PM is 13, 5:30 PM is 17 h 30 m, and 9:15 PM is 21 h 15 m. Midnight (12 AM) is 0 and noon (12 PM) stays 12 — those two are the ones most often reversed. The Time 1 and Time 2 boxes use the 24-hour clock, so entering 5 for 5 PM gives the wrong answer.
Can I use military time like 1730 in this calculator?
Yes, just split it. Military time drops the colon, so 1730 means 17 hours 30 minutes: type 17 in the hours box and 30 in the minutes box. 0045 is 0 hours 45 minutes. The result is shown in both h:m:s and HH:MM:SS digital format, so you can read it back in the same notation.
Does the time calculator handle overnight shifts past midnight?
Yes. In "Duration between two clock times" mode, an end time earlier than the start time is treated as the next day rather than a negative result. A shift from 22:30 to 06:15 returns 7 hours 45 minutes and the result is labelled "next day" so you can confirm it read your shift correctly.
How do I convert 7 hours 45 minutes to decimal hours?
Divide the minutes by 60 and add them to the hours: 7 + (45 / 60) = 7.75. Common values are 15m = 0.25, 20m = 0.33, 30m = 0.50, 40m = 0.67 and 45m = 0.75. Do not write 7.45 for 7h 45m — that means 7 hours 27 minutes, and across a fortnightly timesheet the difference removes close to an hour of paid work.
Is it legal for my employer to round my hours to the quarter hour?
In the United States, yes, provided the rounding is neutral over time. Under 29 CFR 785.48 an employer may record time in quarter-hour increments, but a scheme that consistently rounds in the employer's favour is not permitted. The usual compliant pattern is the 7-minute rule: minutes 1-7 past a quarter round down and 8-14 round up. Keep your exact clock times, because the exact record is what settles a dispute.