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Time Converter

Convert time between nanoseconds, microseconds, milliseconds, seconds, minutes, hours, days, weeks, fortnights, months, years, and decades. Exact SI factors, honest Julian month and year conventions.

h

Result

3,600 s

1 h= 3,600 s

UnitValue
Nanosecond (ns)3.6E12
Microsecond (µs) (µs)3,600,000,000
Millisecond (ms)3,600,000
Second (s)3,600
Minute (min)60
Hour (h)1
Day (24 hours) (day)0.0416667
Week (7 days) (wk)0.00595238
Fortnight (14 days) (fortnight)0.00297619
Month (average, 30.44 days) (mo)0.00136893
Year (Julian, 365.25 days) (yr)1.14077E-4
Decade (10 years) (decade)1.14077E-5

Need the time between two calendar dates instead? Try the date duration calculator.

Mass ConverterUnit Converter

Time converter. Convert nanoseconds, seconds, days, months, years and decades in one tool.

A time converter changes an amount from one time unit to another — from nanoseconds up to decades — by scaling every value through the second. It keeps sub-second and calendar-day units exact and flags month, year and decade results as averages, so you always know which numbers are rounded.

What Is a Time Converter?

Ask the web how many seconds are in a year and you get at least four different answers: 31,536,000 for a plain 365-day year, 31,557,600 for a 365.25-day Julian year, 31,556,952 for the mean Gregorian year, and 31,622,400 for a leap year. None of them is wrong — they just answer slightly different questions. That quiet disagreement is the whole reason a time converter has to be honest about its assumptions instead of picking one number and hiding it. Most converters online do hide it: one popular tool lists a month as 2,628,000 seconds but a year as the Julian 31,557,600 seconds, which means twelve of its own months add up to 31,536,000 — not one of its own years. This converter is built so that never happens.
Every value here pivots through one base unit: the second, the SI base unit of time, defined since 1967 by 9,192,631,770 oscillations of a caesium-133 atom. You enter an amount in any supported unit, it multiplies by that unit's seconds-per-unit factor to reach seconds, then divides by the target unit's factor to land where you want. For the units from nanosecond through fortnight, those factors are exact by definition — a millisecond is exactly one-thousandth of a second, a day is exactly 86,400 seconds, a week is exactly 604,800, and a fortnight (two weeks) is exactly 1,209,600. No rounding, no calendar guesswork.
Month, year and decade are different. A calendar month is 28 to 31 days and a calendar year is 365 or 366, so there is no single exact number of seconds in either. This converter uses the Julian convention — a year of 365.25 days = 31,557,600 seconds, a month of exactly one-twelfth of that = 30.4375 days = 2,629,800 seconds, and a decade of ten years = 315,576,000 seconds. Because the month is defined as the year divided by twelve, twelve months always equal one year exactly, and the tool tags every result that touches these three units with a ≈ sign so you are never misled into thinking an average is exact. The gap matters: a Julian year (31,557,600 s, 8,766 hours) is 21,600 seconds — exactly 6 hours — longer than a plain 365-day common year (31,536,000 s, 8,760 hours), which is the accumulated quarter-day that forces a leap day every four years.
The converter supports twelve units across three families. The sub-second family covers the nanosecond (10⁻⁹ s, the scale of CPU cache latency), microsecond (10⁻⁶ s) and millisecond (10⁻³ s, the scale of network and disk timing). The common family covers the second, minute, hour, day and week. The long-period family covers the fortnight, month, year and decade. What separates a serious time converter from a widget that spits out a number is exactly this: telling you which conversions are exact by definition and which are calendar averages, and keeping those averages internally consistent so twelve months and one year are always the same length.

How to Convert Between Time Units

Every time conversion is one multiplication and one division through the second. The general rule is:
y=x⋅afromatoy = x \cdot \frac{a_{\text{from}}}{a_{\text{to}}}
where x is your input value, a_from is the source unit's value in seconds, and a_to is the target unit's value in seconds. To do it by hand:
1. Look up the source-to-second factor. For hours, a_from = 3,600.
2. Multiply the input by that factor to get seconds. 2.5 hours × 3,600 = 9,000 seconds.
3. Look up the target-to-second factor. For minutes, a_to = 60.
4. Divide the seconds by the target factor. 9,000 ÷ 60 = 150 minutes.
The same two steps work for any pair. Milliseconds to days: 500,000,000 ms × 0.001 s/ms ÷ 86,400 s/day = 5.787 days. Nanoseconds to seconds: 750,000 ns × 0.000000001 s/ns = 0.00075 s (which is also 0.75 ms). Fortnight to hours: 1 fortnight × 1,209,600 s ÷ 3,600 s/hour = 336 hours.
To use the calculator, pick the source unit from the From dropdown, type a value, then pick the target unit from the To dropdown. The result updates as you type, and you can click it to copy. Very large or very small results switch to scientific notation automatically, so converting a nanosecond to a decade still reads cleanly instead of showing a wall of zeros. Any result that involves a month, year or decade carries a ≈ mark, because those three units are calendar averages rather than exact definitions — everything from nanoseconds through fortnights is exact.

Worked Time Conversion Examples

5,400 seconds to hours (workout and sleep-cycle math)

Set From = Second, To = Hour, Value = 5,400. The result is 5,400 ÷ 3,600 = 1.5 hours, which is also 90 minutes. This is the canonical conversion behind a 90-minute sleep cycle or a 5,400-second timer: 1.5 hours reads as 1 hour and 30 minutes on a clock. The conversion is exact because both the second and the hour (3,600 s) are exact definitions — no calendar averaging is involved.

500 million milliseconds to days (log and timestamp math)

Set From = Millisecond, To = Day, Value = 500,000,000. The result is 500,000,000 ÷ 86,400,000 = 5.787 days, because one day is exactly 86,400,000 milliseconds (86,400 s × 1,000). Developers hit this constant constantly: JavaScript and Java timestamps count milliseconds from the 1970 Unix epoch (Unix time itself counts seconds), so dividing a millisecond difference by 86,400,000 turns it into days. The conversion is exact — no year length or month average is involved.

How many seconds are in a year (the honest answer)

Set From = Year, To = Second, Value = 1. The result is ≈ 31,557,600 seconds, the Julian year of 365.25 days (365.25 × 86,400). A plain 365-day common year is 31,536,000 seconds instead — 21,600 seconds, or exactly 6 hours, shorter. That 6-hour gap per year is the quarter-day that accumulates into a leap day every four years. This converter shows the Julian figure with a ≈ because it is a long-term average, not the exact length of any single calendar year.

Nanoseconds to seconds for benchmarking

Set From = Nanosecond, To = Second. A function that runs in 750,000 ns converts to 0.00075 s, which is easier to read as 0.75 ms. This is the everyday work of performance analysis, where the raw numbers span a huge range: an L1 cache hit is around 1 ns, a main-memory reference around 100 ns, an SSD read around 100,000 ns (0.1 ms), and a data-center network round trip around 100,000 to 300,000 ns (0.1 to 0.3 ms). Sub-second conversions here are exact, because the nanosecond, microsecond and millisecond are exact SI submultiples of the second.

One billion seconds to years (a scientific-notation check)

Set From = Second, To = Year, Value = 1,000,000,000. The result is ≈ 31.69 years (1,000,000,000 ÷ 31,557,600). In other words, you pass your one-billionth second of life at roughly 31 years and 8 months old — a milestone worth a small celebration. The ≈ appears because the answer depends on the year length; with a plain 365-day year the same billion seconds works out to about 31.71 years. The difference is tiny here but grows for very large inputs, which is exactly why the convention has to be stated instead of assumed.

Comparative table: 1 unit expressed in seconds

This table is the backbone of every conversion the tool performs. To convert by hand between any two units, take the source row's seconds and divide by the target row's seconds.
Unit1 unit in secondsExact?
Nanosecond0.000000001yes
Microsecond0.000001yes
Millisecond0.001yes
Second1yes
Minute60yes
Hour3,600yes
Day86,400yes
Week604,800yes
Fortnight1,209,600yes
Month2,629,800≈ (Julian)
Year31,557,600≈ (Julian)
Decade315,576,000≈ (Julian)
For example, 1 week in minutes = 604,800 ÷ 60 = 10,080 minutes, and 1 year in hours = 31,557,600 ÷ 3,600 = 8,766 hours. The consistency check that trips up rival tools also lives here: 12 × 2,629,800 = 31,557,600, so twelve months equal one year exactly. Every long-period row (month, year, decade) is an average, marked ≈; every row above it is exact.

Most-Searched Time Conversions at a Glance

FromToValueExact?
1 minuteseconds60yes
1 hourseconds3,600yes
1 dayseconds86,400yes
1 daymilliseconds86,400,000yes
1 weekhours168yes
1 fortnightseconds1,209,600yes
1 secondmilliseconds1,000yes
1 secondnanoseconds1,000,000,000yes
1 monthseconds2,629,800≈ Julian
1 yearseconds31,557,600≈ Julian
1 yearhours8,766≈ Julian
1 decadedays3,652.5≈ Julian

Time Converter — Frequently Asked Questions

How many seconds are in a year?

This converter uses ≈ 31,557,600 seconds, the Julian year of 365.25 days that averages in leap years. A plain 365-day common year is 31,536,000 seconds instead — 21,600 seconds (exactly 6 hours) shorter. The larger figure is the better choice for long-term averages, which is why most general-purpose and scientific converters default to it.

How many milliseconds are in a day?

Exactly 86,400,000 milliseconds. One day is 86,400 seconds (24 × 3,600), and each second holds 1,000 milliseconds, so 86,400 × 1,000 = 86,400,000. This value is exact — no calendar averaging is involved.

How many seconds are in a fortnight?

Exactly 1,209,600 seconds. A fortnight is two weeks, or 14 days, and 14 × 86,400 = 1,209,600. It is one of the exact units in this converter, along with everything from nanoseconds up through weeks.

How do I convert nanoseconds to seconds?

Divide by one billion. A nanosecond is 10⁻⁹ seconds, so 750,000 ns ÷ 1,000,000,000 = 0.00075 s. In the tool, set From = Nanosecond and To = Second; large or small results switch to scientific notation automatically.

Why does this converter use 365.25 days for a year?

Because 365.25 days (the Julian year) is the simplest average that accounts for leap years, and it keeps the tool internally consistent: the month is defined as exactly one-twelfth of the year (30.4375 days = 2,629,800 seconds), so twelve months always equal one year exactly. Many other converters mix a 365-day-based month with a 365.25-day year, which quietly breaks that identity. Because 365.25 is still an average, month, year and decade results are all shown with a ≈ mark.

Which conversions are exact and which are approximate?

Everything from nanosecond through fortnight is exact — these units are integer or power-of-ten multiples of the second (a day is exactly 86,400 s, a week 604,800 s, a fortnight 1,209,600 s). Month, year and decade are calendar averages under the Julian convention, so any result that touches those three units is flagged with ≈. If a conversion has no ≈, you can treat it as exact by definition.

What is the difference between this and a date duration calculator?

A time converter changes an amount between units — "5,400 seconds is how many hours?" — using fixed average factors. A date duration calculator measures the real gap between two calendar dates, such as March 3 to June 1, honoring the actual lengths of the months in between and any leap day. Use this converter when you have a raw quantity of time; use the date duration calculator when you have two specific dates and need the exact interval.

Why do different websites give different numbers for a year in seconds?

Because they answer different questions. A 365-day common year is 31,536,000 seconds, a 365.25-day Julian year is 31,557,600, the mean Gregorian year (365.2425 days) is 31,556,952, and a 366-day leap year is 31,622,400. All are correct for their own definition. This converter states its choice — the Julian year — openly and marks it ≈ so you are never guessing which one you got.

How many hours are in a year?

About 8,766 hours under the Julian convention (365.25 × 24), which is what this converter reports. A plain 365-day year is 8,760 hours, and a 366-day leap year is 8,784 hours. The everyday classroom answer is 8,760; the leap-year-averaged answer is 8,766.

Is this time converter free?

Yes. It runs entirely in your browser with no account and no usage limits, and it handles the full range from nanoseconds to decades. The same tool is available as an embeddable widget, so a programming blog, science-teaching page or ops runbook can host it without sending readers off-site.

How accurate is this converter?

For every unit from nanosecond through fortnight, the factors are exact by definition, so those conversions carry no rounding beyond your chosen display precision. For month, year and decade, the tool uses the Julian averages (year = 365.25 days, month = year ÷ 12) and marks every affected result with ≈, because no calendar month or year has a single exact length. For the precise gap between two real dates, use a date duration calculator instead.

Content verified by the Smart Calculators Team