Time Calculator – Hours, Minutes & Seconds

Time Calculator – Add, Subtract and Convert Time

This free time calculator adds and subtracts hours, minutes and seconds, works out the time between two clock times, adds a duration to any date and time, and converts between decimal hours and hours-and-minutes. It is designed for everyday jobs that are surprisingly fiddly by hand: adding up timesheet hours, working out a shift length with an unpaid break, finding what time it will be in 8 hours and 30 minutes, totalling video or workout durations, or turning 7.75 hours into 7 hours 45 minutes for payroll.

Time does not work in base 10 – there are 60 minutes in an hour and 60 seconds in a minute – so a normal calculator gives the wrong answer if you simply add 1.45 and 2.30. This calculator carries the minutes and seconds over correctly, shows every result in several formats at once, and handles night shifts that cross midnight.

How to Use the Time Calculator

1. Add durations: enter hours, minutes and seconds in each row. Tap the sign button to subtract a row instead. Add as many rows as you need – the total appears instantly.
2. Time between: enter a start and end time, an unpaid break, and optionally your hourly rate. You get the hours worked in h:mm and decimal, and your pay for the shift.
3. Add to a time: choose a start date and time (or tap Now), pick Add or Subtract and enter the duration. The result shows the new date, time and day of the week.
4. Decimal ↔ h:mm: type decimal hours such as 7.75 or a time such as 7:45; the other box converts automatically.

How Time Addition Works

To add times by hand, add the seconds, minutes and hours separately, then carry over: every 60 seconds becomes a minute and every 60 minutes becomes an hour. For example:

2 h 45 m + 1 h 30 m = 3 h 75 m = 4 h 15 m

Subtraction works the other way – if you do not have enough minutes, borrow 60 minutes from the hours. 5 h 10 m − 2 h 40 m becomes 4 h 70 m − 2 h 40 m = 2 h 30 m. The calculator does this automatically and never shows negative minutes.

Converting Between Decimal Hours and Minutes

Payroll systems and invoices often use decimal hours, while clocks show hours and minutes. To convert, multiply the decimal part by 60; to go back, divide the minutes by 60.

Minutes = decimal part × 60 · Decimal hours = hours + minutes ÷ 60

Example: 7.75 hours = 7 hours + 0.75 × 60 = 7 hours 45 minutes. 8 hours 20 minutes = 8 + 20 ÷ 60 = 8.33 hours. A very common mistake is to read 7.30 hours as 7 hours 30 minutes – it is actually 7 hours 18 minutes.

Minutes	Decimal hours	Minutes	Decimal hours
5	0.08	35	0.58
10	0.17	40	0.67
15	0.25	45	0.75
20	0.33	50	0.83
25	0.42	55	0.92
30	0.50	60	1.00

Calculating Hours Worked

To work out the length of a shift, subtract the start time from the end time and take off any unpaid break. A shift from 9:00 to 17:30 with a 30-minute lunch is 8 hours 30 minutes minus 30 minutes = 8 hours (8.00 decimal). If the shift runs past midnight, for example 22:00 to 06:00, add 24 hours to the end time: 30:00 − 22:00 = 8 hours. The Time between mode does this for you and also shows the pay when you enter an hourly rate.

Shift	Break	Hours worked	Decimal
09:00 – 17:00	1 hour	7 h 00 m	7.00
09:00 – 17:30	30 min	8 h 00 m	8.00
08:15 – 16:45	45 min	7 h 45 m	7.75
07:00 – 19:00	1 hour	11 h 00 m	11.00
22:00 – 06:00	30 min	7 h 30 m	7.50

Adding Hours to a Date and Time

Need to know when a 36-hour delivery window ends, when to take the next dose of medicine, what time a 14-hour flight lands in departure-city time, or when a 72-hour return period expires? Use Add to a time. The calculator adds days, hours, minutes and seconds to your start date and time and shows the new date, time and weekday. It works in your device's local time.

The 24-Hour Clock and AM/PM

The 24-hour clock runs from 00:00 (midnight) to 23:59. It is standard in the military, transport timetables, hospitals and most countries outside North America because it avoids AM/PM confusion. To convert afternoon times from the 24-hour clock, subtract 12: 15:45 is 3:45 PM. Midnight is 12:00 AM (00:00) and noon is 12:00 PM (12:00).

24-hour	12-hour	24-hour	12-hour
00:00	12:00 AM	12:00	12:00 PM
03:00	3:00 AM	15:00	3:00 PM
06:30	6:30 AM	18:30	6:30 PM
09:15	9:15 AM	21:15	9:15 PM

Time Units at a Glance

Unit	Equals
1 minute	60 seconds
1 hour	60 minutes = 3,600 seconds
1 day	24 hours = 1,440 minutes = 86,400 seconds
1 week	7 days = 168 hours = 10,080 minutes
1 year (365 days)	8,760 hours = 525,600 minutes

Everyday Uses of a Time Calculator

• Timesheets and payroll: add daily hours for a weekly total and convert to decimal for pay.
• Freelancers and consultants: total billable time across tasks and multiply by your rate.
• Video, audio and podcasts: add clip lengths in minutes and seconds to get the running time.
• Sport and fitness: total split times for running, cycling or swimming, and compare laps.
• Cooking and baking: work back from a serving time to find when to start each step.
• Travel: total layovers and flight times, or find a landing time after a long flight.
• Studying: track revision hours towards a weekly target.

Weekly Hours and Overtime

To total a working week, add each day's hours in Add durations mode – one row per day. The result shows the weekly total in hours and minutes and in decimal hours, ready for a timesheet. In the UK, the Working Time Regulations limit average working time to 48 hours a week unless you opt out, and in the US the Fair Labor Standards Act requires overtime at 1.5 times the regular rate for non-exempt employees after 40 hours in a workweek. Knowing your exact total helps you check your payslip.

Example: Totalling a Weekly Timesheet

Here is a typical week for a part-time worker. Enter each day as one row in Add durations, or work out each shift first in Time between.

Day	Start – end	Break	Hours	Decimal
Monday	09:00 – 15:15	30 min	5 h 45 m	5.75
Tuesday	09:00 – 14:00	none	5 h 00 m	5.00
Wednesday	12:30 – 20:10	40 min	7 h 00 m	7.00
Thursday	09:00 – 13:20	none	4 h 20 m	4.33
Friday	08:45 – 15:00	30 min	5 h 45 m	5.75
Total			27 h 50 m	27.83

Notice that adding the decimal column gives 27.83, the same as 27 hours 50 minutes (50 ÷ 60 = 0.83). If you had added the minutes as if they were decimals you would get a wrong total – a common cause of payslip errors.

Time Zones and Daylight Saving

The Add to a time mode uses the time zone set on your device. If your period crosses the start or end of daylight saving time, the clock time will jump by an hour – for example, adding 24 hours on the night the clocks go forward gives a clock time one hour later than the day before. That is correct: 24 real hours have passed. To find the local arrival time of a flight in another country, first add the flight time in your departure time zone, then add or subtract the time difference to the destination. Remember that the UK and Europe change their clocks on different dates from the United States in March and October/November.

Common Mistakes When Calculating Time

• Treating minutes as decimals. 1.30 + 1.45 is not 2.75 hours – it is 1 h 30 m + 1 h 45 m = 3 h 15 m (3.25 hours).
• Forgetting the break. Unpaid breaks must be taken off before calculating pay.
• Getting night shifts wrong. A shift from 22:00 to 06:00 is 8 hours, not −16 hours.
• Rounding too early. Round only the final total; rounding each day to the nearest quarter hour can add up to a noticeable error over a month.
• Mixing 12- and 24-hour times. 7:00 could be morning or evening – use the 24-hour clock for shifts.

Frequently Asked Questions