acalculator

How to convert time to decimal?

Enter hours, minutes and seconds to get decimal hours, or switch to decimal to time to turn a number like 7.75 back into hours and minutes.

Your numbers

Convert
Decimal hours
7.75

7:45:00 is 7.75 hours.

As h:mm:ss
7:45:00
Decimal minutes
465
Seconds
27,900

Decimal hours: 7.75. 7:45:00 is 7.75 hours.

How to calculate

Converts hours, minutes, and seconds to decimal hours (7:45 is 7.75 hours), and decimal hours back to hours, minutes, and seconds.

Example with the default inputs (Convert Time to decimal, Hours 7, Minutes 45, Seconds 0): 7:45:00 is 7.75 hours.

Method: decimal hours = hours + minutes ÷ 60 + seconds ÷ 3,600; back: seconds = decimal hours × 3,600, split into hours, minutes, and seconds

  • An hour is 60 minutes and a minute is 60 seconds.
  • Converting a time, the hours, minutes, and seconds are whole numbers; minutes and seconds may be 60 or more.
  • Converting decimal hours, the time is rounded half up to the nearest millisecond.

Machine-readable copies: Markdown, JSON.

Worked examples

Each example is checked against the calculator on every build.

  1. Convert Time to decimal, Hours 7, Minutes 45, Seconds 0 gives Decimal hours 7.75, As h:mm:ss 7:45:00, Decimal minutes 465, Seconds 27,900.Source: SI Brochure (BIPM, 9th edition, 2019), Table 8: 1 h = 60 min = 3,600 s
  2. Convert Time to decimal, Hours 1, Minutes 20, Seconds 15 gives Decimal hours 1.3375, As h:mm:ss 1:20:15, Decimal minutes 80.25, Seconds 4,815.Source: SI Brochure (BIPM, 9th edition, 2019), Table 8
  3. Convert Time to decimal, Hours 0, Minutes 90, Seconds 0 gives Decimal hours 1.5, As h:mm:ss 1:30:00.
  4. Convert Decimal to time, Decimal hours 1.2345 gives Time 1 hour, 14 minutes, 4.2 seconds, As h:mm:ss 1:14:04.2, Decimal minutes 74.07, Seconds 4,444.2.Source: SI Brochure (BIPM, 9th edition, 2019), Table 8
  5. Convert Decimal to time, Decimal hours 0.3 gives Time 18 minutes, As h:mm:ss 0:18:00, Seconds 1,080.

How it works

Time to decimal. Hours, minutes and seconds are whole numbers of 0 or more; minutes and seconds may be 60 or more. With T = hours × 3,600 + minutes × 60 + seconds (the time in seconds):

  • Decimal hours = T ÷ 3,600.
  • Decimal minutes = T ÷ 60.
  • Seconds = T.
  • As h:mm:ss = the time written as hours:minutes:seconds, with the hours whole and not padded, and the minutes and seconds each under 60 and written with 2 digits: T = 4,815 is 1:20:15.

Decimal to time. Decimal hours is a number of 0 or more. First the time in whole milliseconds: ms = decimal hours × 3,600,000, rounded half up to a whole number. Then:

  • Time: hours = ms ÷ 3,600,000 rounded down; minutes = what is left ÷ 60,000 rounded down; seconds = what is left after that ÷ 1,000 (it can have up to 3 decimal places).
  • Decimal hours = the number you typed.
  • Decimal minutes = ms ÷ 60,000.
  • Seconds = ms ÷ 1,000.
  • As h:mm:ss = H:MM:SS as above, and when the seconds have a fraction, a point and the milliseconds with trailing zeros removed: 4,444,200 ms is 1:14:04.2.

Decimal hours and decimal minutes show to 4 decimal places and seconds to 3, each rounded half up.

Worked examples by hand

7 hours 45 minutes. T = 7 × 3,600 + 45 × 60 = 27,900 seconds. 27,900 ÷ 3,600 = 7.75 hours, 27,900 ÷ 60 = 465 minutes, written 7:45:00.

1 hour 20 minutes 15 seconds. T = 3,600 + 1,200 + 15 = 4,815 seconds. 4,815 ÷ 3,600 = 1.3375 hours, 4,815 ÷ 60 = 80.25 minutes, written 1:20:15.

90 minutes. T = 5,400 seconds = 1.5 hours, written 1:30:00.

1.2345 hours to a time. 1.2345 × 3,600,000 = 4,444,200 ms. 4,444,200 ÷ 3,600,000 = 1 hour, leaving 844,200 ms; 844,200 ÷ 60,000 = 14 minutes, leaving 4,200 ms = 4.2 seconds. So 1 hour, 14 minutes, 4.2 seconds, written 1:14:04.2, or 74.07 minutes, or 4,444.2 seconds.

0.3 hours to a time. 0.3 × 3,600,000 = 1,080,000 ms = 18 minutes, written 0:18:00.

Other questions people ask

How do I convert time to decimal hours?

Divide the minutes by 60 and the seconds by 3,600, and add them to the hours. 7 hours 45 minutes is 7 + 45 ÷ 60 = 7.75 hours.

How do I convert decimal hours back to hours and minutes?

Keep the whole hours and multiply the decimal part by 60 for minutes. 7.75 hours is 7 hours and 0.75 × 60 = 45 minutes. If the minutes have a decimal part, multiply that by 60 for seconds.

Why do timesheets use decimal hours?

Pay is hours × hourly rate, and that needs hours as one number. 7 hours 45 minutes at $20 an hour is 7.75 × 20 = $155, not 7.45 × 20.

What are common minutes in decimal hours?

15 minutes is 0.25 hours, 30 minutes is 0.5, 45 minutes is 0.75, 20 minutes is 0.3333, 10 minutes is 0.1667, 6 minutes is 0.1, and 1 minute is 0.0167 hours to 4 decimal places.

Can I enter 90 minutes?

Yes. Minutes and seconds may be 60 or more. 0 hours and 90 minutes is 1.5 hours, shown as 1:30:00.

How precise is the result?

Decimal hours and decimal minutes show to 4 decimal places, rounded half up. A time from decimal hours is rounded half up to the nearest millisecond.