Time conversions for timesheets, workouts and deadlines
Time feels like the simplest unit to convert, until you need a precise answer — how many billable hours is 254 minutes, or what a 3:45:12 marathon is in total seconds. The tool above converts between femtoseconds and millennia, and this page covers the conversions that come up in work, sport and computing, plus the quirks (leap years, "fortnight", the fuzzy length of a month) that make time less regular than it looks.
Three real conversions you'll likely do this month
- Timesheets: You logged 254 minutes on a project. 254 ÷ 60 = 4.23 hours — that's 4 hours and 14 minutes, not 4 hours 23. Type 254 minutes into the tool and read the hours.
- Workout splits: A runner's 5 km personal best of 24:36 is 1,476 seconds. Divide by 5 for an average pace of 295.2 seconds per kilometre (4:55 per km), or convert to minutes for a pacing chart.
- Project deadlines: A job due in 3 weeks is 504 hours or 30,240 minutes. Knowing the total hours makes it easier to split work across days without underestimating.
The units this tool covers, second to millennium
On the small end: femtoseconds (10−15 s), picoseconds, nanoseconds and microseconds are the timescales of computer hardware — a nanosecond is about how long light takes to travel one foot. On the everyday end, the standard relationships are exact:
| Base Unit | To Unit | Exact Value |
|---|---|---|
| 1 Minute | Seconds | 60 |
| 1 Hour | Minutes | 60 |
| 1 Day | Hours | 24 |
| 1 Week | Days | 7 |
| 1 Fortnight | Days | 14 |
| 1 Year | Days | 365 (366 in leap years) |
Why a month and a year aren't clean numbers
Months are where the tool makes a deliberate choice. Calendars vary between 28 and 31 days, so this converter uses the average length of a Gregorian calendar year — 365.2425 days — divided by 12, giving a month of 30.44 days (2,629,746 seconds). Likewise a "year" here is 365.2425 days. That's why leap years exist at all: the Earth takes about 365.24 days to orbit the Sun, so we add February 29 roughly every four years to stop the calendar drifting through the seasons.
Micro-time: below the second
- Millisecond (ms): One-thousandth of a second — internet ping and camera shutter speeds.
- Microsecond (μs): One-millionth of a second — CPU clock cycles and high-frequency trading.
- Nanosecond (ns): One-billionth of a second — light travels about a foot per nanosecond.
Time questions that keep coming up
How many hours are in exactly one week?
168 hours — 24 × 7. Over a standard working year of 52 weeks that's 8,736 hours.
What is a fortnight?
Exactly 14 days, or two weeks. The word comes from the Old English "fēowertīne niht" (fourteen nights), and it survives mainly in British payroll, holidays and the odd sporting schedule.
Why is a decade used less than "10 years" in computing?
It's mostly a matter of units. The tool gives exact decade/millennium values because history and astronomy use them; for modern purposes most people convert within seconds, minutes and hours, which are the units shown above.
How do I convert "1 year 3 months" into days?
Using the average-year convention: 1 year (365.24 days) + 3 months (3 × 30.44 = 91.3 days) ≈ 456.5 days. For payroll or legal deadlines, always use the calendar-specific count instead — the tool's average is a planning number, not a legal one.