Time Unit Converter

What this converter does

Every duration is one number wearing different units, and this converter shows the whole wardrobe at once: enter anything from nanoseconds to centuries, or a clock time as hours, minutes and seconds, and get back the exact total in seconds, a human breakdown in mixed units, the clock-time form, and a table of the value in all twelve units at the precision you choose. It handles the two jobs that make time conversion a real task rather than a party trick: decimal hours for payroll and billing, where 7:45 must become 7.75 and 1.30 must not be mistaken for an hour and thirty, and signed durations, where a negative time is a real thing that deserves real conversions instead of an error message.

How to use it

1. Two ways in. “A value in one unit” is for quantities: 90 minutes, 2.5 days, 10,000,000 seconds. “Hours : minutes : seconds” is for clock readings copied off a timesheet or a stopwatch. They meet in the middle: both become a total in seconds, and every output is derived from that total, so the two entry styles can be used to check each other.
2. Decimal hours are not clock time, and the difference costs money. 1.5 hours is 1 hour 30 minutes. 1.30 hours is 1 hour 18 minutes. The two look similar on a payslip and differ by twelve minutes of pay. Payroll systems want decimals; humans read clocks; this page converts in both directions and the worked examples below pin the trap down with the exact figures.
3. Precision is a display choice, not a rounding of the truth. The exact total in seconds always prints at full precision. The table rounds to the decimal places you select, because 0.0089 weeks is information and 0.008928571428571429 weeks is noise. Very large and very small values switch to scientific notation automatically, since 5,400,000,000,000 nanoseconds is readable and its table-mates at the tiny end would otherwise be rows of zeros.
4. Negative durations are entered with the tick. Tick the box and the magnitude you entered is treated as negative throughout: table, breakdown and clock form all carry the sign. This is for time owed, offsets from a reference, countdowns that ran past zero and timezone-style differences, all of which are legitimate arithmetic that many converters refuse to touch.
5. Months and years are averages here, on purpose. A converter needs fixed sizes, so a year is the Julian year, 365.25 days, the scientific convention that folds leap years in, and a month is exactly a twelfth of it, 30.436875 days. Calendar questions (how many days between two dates, what date is 90 days from now) belong to the Date Calculator, which knows which month you mean. This page’s disclaimer says the same, in the small print where it belongs.
6. Fields in the clock entry may overflow honestly. Entering 90 in the minutes field gives an hour and a half, not an error: durations are not clock faces, and normalising them is the page’s job.

How it is calculated

Everything converts through total seconds. Clock entry: total = hours x 3600 + minutes x 60 + seconds. Decimal hours are that total divided by 3600, which is why 1.30 hours (4,680 seconds) breaks down as 1 hour and 18 minutes, not 1 hour 30. Unit sizes in seconds: minute 60, hour 3,600, day 86,400, week 604,800, average month 2,629,800, Julian year 31,557,600, decade and century by tens. The breakdown takes the largest units first, greedily, the way people naturally say durations. Values are computed at full precision and rounded only for display.

Worked examples

The validation case: 1 hour 30 minutes entered as a clock time: total 5,400 seconds, 90 minutes, 1.5 hours, 0.0625 days, 0.0089 weeks at four decimal places, and 5,400,000,000,000 nanoseconds. One duration, six costumes, all consistent.

The payroll trap, disarmed: 1.30 in the amount field with Hours as the unit: 4,680 seconds, breakdown 1 hour, 18 minutes. Anyone who has ever read 1.30 as “one thirty” now has the page to point at. And the reverse journey: 7 hours 45 minutes on a timesheet is 27,900 seconds, which the table reports as 7.75 hours, the number the payroll system actually wants.

The big breakdown: 10,000,000 seconds is the kind of figure that means nothing until it is decomposed: 3 months, 3 weeks, 3 days, 10 hours, 16 minutes, 40 seconds on this page’s average months, roughly a season and change. This is the answer to every “how long is a million seconds” question (11 days, 13 hours, 46 minutes, 40 seconds, since you ask, and a billion seconds is nearly 32 years).

A negative case: 90 minutes with the negative tick: -5,400 seconds, -1.5 hours, breakdown -1 hour, 30 minutes. A shift swapped, a debt of time, an offset: the sign survives every conversion, which is the entire point.

Two and a half days: 60 hours, 3,600 minutes, 216,000 seconds, 0.3571 weeks. Weeks are the unit nobody can do in their head, which is why they are in the table.

Reading your result

Start with the breakdown for comprehension and the table for work. The breakdown is how you would say the duration to a person; the table is how you paste it into a spreadsheet, a bid, or a piece of code. If a figure will be re-entered somewhere else, take it from the exact-seconds line or the highest-precision table, not from a rounded cell: chained rounding, converting a rounded value again, is how small errors are manufactured. And remember what the month and year rows are: averages, excellent for estimating and planning, wrong for anything with a calendar date attached.

Limitations

• Calendar time is not converted here. Months of 28 to 31 days and leap years make calendar durations depend on when they start. This page’s fixed averages cannot know that, and date-to-date questions belong to the Date Calculator.
• No time zones, no daylight saving. A duration is a duration everywhere; the moment a duration is pinned to a clock on a wall in a place, zones and DST enter, and that is date arithmetic again, deliberately out of scope.
• Extreme precision is display, not measurement. The converter will happily express a year in nanoseconds; the figure is exact arithmetic on the input, and says nothing about how precisely any real duration was measured.
• Payroll rounding rules belong to employers and law. Many workplaces round clock times to the nearest quarter hour under specific rules before decimal conversion. This page converts exactly what you enter; applying a rounding policy first is a separate, documented step, and the Work Hours Calculator on this site handles timesheets as a whole.

Frequently asked questions

How do I convert minutes to decimal hours for payroll?

Divide the minutes by 60: 45 minutes is 0.75 hours, 20 minutes is 0.33 recurring (enter it here and take the table’s hours row at the precision your payroll uses). For a full clock time, convert hours and minutes together: 7 hours 45 minutes is 7.75. This page’s clock entry exists for exactly this: type the timesheet reading in, read the decimal off the Hours row, and use the breakdown line to check you typed what you meant.

Why is 1.30 hours not 1 hour 30 minutes?

Because the .30 is three tenths of an hour, and three tenths of 60 minutes is 18 minutes. Clock notation divides the hour into 60 parts; decimal notation divides it into 100. The two systems collide on payslips constantly, and the collision always favours whoever is not checking. 1 hour 30 minutes in decimal is 1.5, written 1.50: notice that the honest decimal carries its meaning in the second digit, where the trap figure 1.30 hides.

How many seconds are in a year?

31,557,600 on the Julian year used here (365.25 days, accounting for leap years on average), or 31,536,000 in a plain 365-day year. The 21,600-second difference, six hours, is the leap-year quarter day, and which figure you want depends on whether your span includes the leap days the average assumes. Both are in reach of this page: enter 1 in Years, or 365 in Days, and compare the Seconds rows.

Can it convert time for video or audio work?

Yes, durations are durations: a 2.5-hour render, a 95-minute master, frame counts at a fixed rate converted to seconds first (frames divided by frames per second) all pass through the same table. What it does not carry is drop-frame timecode, which is a labelling system with its own rules rather than a duration, and is out of scope here.

Related calculators

• All Everyday and Time Calculators
• Work Hours Calculator
• Time Calculator
• Date Calculator

Method: all conversions through total seconds at full precision, display rounded to the selected precision; year defined as the Julian year (365.25 days) and month as its twelfth, both stated on the page; negative durations carried through every output. Last reviewed: 13 October 2026.