Time to Decimal Calculator

decimal hours = hours + minutes ÷ 60 + seconds ÷ 3600, computed on the total second count so that the arithmetic stays exact

hours

The whole hours, with no upper limit — a month of work is around 170 and a year is around 2000

minutes

0 to 59. Sixty minutes is one hour and has to be entered in the hours box instead

seconds

0 to 59, for a time clock that records seconds. Leaving it at zero is the usual case

decimalHours

The result: the whole span expressed in hours, rounded to two decimal places for display

totalMinutes

The same span counted in minutes, rounded to a whole minute. 7 h 45 m is 465 minutes

totalSeconds

The same span in seconds, exact whenever the three inputs are whole numbers — this is the row that shows what the rounding did

Use it at the point where a duration has to meet a rate: a payslip, a client invoice billed by the hour, a timesheet that will only accept a number, or a project estimate that multiplies hours by a cost. The three inputs are also the fastest way to check a conversion in the other direction — if a payroll system reports 7.76 hours, entering 7 hours 45 minutes and 20 seconds shows where that came from. If you have two clock times rather than a duration, the time duration calculator gives the duration first; if the number is already decimal and you want it back as hours and minutes, that is the decimal to time direction.

1. A timesheet line of 7 hours 45 minutes

   1. The span is 7 whole hours plus 45 minutes, so the decimal form keeps the 7 and converts the remainder
   2. 45 ÷ 60 = 0.75, so 7 + 0.75 = 7.75 decimal hours
   3. Counted in minutes the same span is 7 × 60 + 45 = 465, and in seconds 465 × 60 = 27900
   4. Multiplying 7.75 by an hourly rate gives the same amount as multiplying 465 minutes by the rate per minute

   At 20 an hour this line is 155, which is the arithmetic the conversion exists to make possible; the reverse page takes 7.75 back to 7 hours 45 minutes.

2. Half an hour on its own

   1. There are no whole hours, so the decimal form is entirely the minutes
   2. 30 ÷ 60 = 0.5 decimal hours
   3. The minute row is unchanged at 30, and the seconds row is 30 × 60 = 1800
   4. A zero in the hours box is a real zero here, not an empty field

   Half an hour is 0.5 rather than 0.30: decimal hours divide the hour into hundredths, so the minutes have to be divided by sixty rather than moved two places.

3. The last second of a day

   1. 23 hours 59 minutes 59 seconds is one second short of a full day
   2. In seconds that is 23 × 3600 + 59 × 60 + 59 = 82800 + 3540 + 59 = 86399
   3. Divided by 3600 the exact value is 23.99972, which the two-decimal display rounds up to 24
   4. The minute row rounds the same way, from 1439.98 to 1440

   The two rounded rows both read as a full day while the exact row says 86399 seconds. That is what two decimal places do, and it is the reason the seconds row is worth keeping in view when the exact value matters.

The hours figure is rounded to two decimal places for display, so a span like 23:59:59 reads as 24.00 even though it is one second short of a day; the seconds row carries the exact value. Rounding to two decimals can overstate a block of time by up to 0.005 hours, which is 18 seconds, so a month of daily lines can drift by a couple of minutes in total if each line is rounded rather than the sum. Only whole hours, minutes and seconds are accepted — there is no way to type 7.5 hours plus 30 minutes — and negative values are refused rather than treated as time owed. No break is deducted, the pay rate is not part of the calculation, and nothing here knows about dates or time zones.

What are decimal hours?

Decimal hours are a duration written as a plain number of hours, so 7 hours 45 minutes is 7.75 and half an hour is 0.5. The minutes are divided by sixty rather than moved two decimal places, which is why 45 minutes is 0.75 rather than 0.45. Multiplying decimal hours by an hourly rate gives the pay directly, which is the reason timesheets use them.

How do I convert 45 minutes to a decimal?

Divide by 60: 45 ÷ 60 = 0.75. The same rule gives 15 minutes as 0.25, 30 minutes as 0.5 and 6 minutes as 0.1 of an hour, which is the smallest fraction many time clocks record. Rounding to the nearest tenth of an hour is a long-standing payroll practice, and one-tenth of an hour is six minutes.

Why can't I enter 90 minutes?

Because 90 minutes is not a time, it is a carry: 90 minutes is 1 hour 30 minutes, and the boxes are meant to hold the parts of a time rather than a running total. Minutes and seconds stop at 59 so that 7 hours 60 minutes is refused instead of being quietly read as 8 hours. Enter the carry in the hours box: 1 hour 30 minutes, not 0 hours 90 minutes.

Why does 23:59:59 come out as 24.00 hours?

Because the display is rounded to two decimal places: 86399 seconds is 23.99972 hours, which rounds up to 24.00. The exact value is still there in the seconds row. Two decimal places is the usual payroll convention and the error is at most 18 seconds per line, but if a number has to be exact, use the seconds row rather than the rounded hours.

How does this connect to overtime pay?

Decimal hours are what an overtime rule is applied to: in the United States, hours worked beyond forty in a workweek must be paid at not less than one and a half times the regular rate, and a rule like that needs the week expressed as one number. Convert each day to decimal hours, add the days up, and the part above forty is the overtime. This page converts a single duration; adding a week up is the hours calculator's job.

• 29 C.F.R. § 785.48 — Rounding practices — Office of the Federal Register
• 29 U.S.C. § 207 — Maximum hours and overtime compensation — Legal Information Institute, Cornell Law School
• RFC 3339: Date and Time on the Internet: Timestamps — IETF