⏱️ Time

Time Converter

From nanoseconds to centuries — convert any duration into the unit you think in. Type a value, choose the units and press Convert.

Written and reviewed by SM Arijul Islam · Last reviewed 28 October 2026 · Editorial standards · Report an error

About the time converter

The second is the SI base unit of time and is defined by the caesium atomic clock. Everything else — minutes, hours, days — is a human convention, which is why months and years need care: they are averaged here to keep the maths consistent.

Factors used

1 minute = 60 s · 1 hour = 3,600 s · 1 day = 86,400 s
1 week = 7 days · 1 fortnight = 14 days
1 month (average) = 30.43685 days
1 year (Gregorian average) = 365.2425 days
1 millisecond = 0.001 s · 1 microsecond = 0.000001 s

Need a countdown between two real dates? Use the Date Calculator or the Age Calculator.

How to convert time

Time units run from nanoseconds to millennia. The second is the SI base unit, defined by caesium atomic vibrations. Minutes and hours sit outside SI but are universally used, a standard day is 86,400 seconds, and a year is normally 365 days with leap days keeping the calendar aligned to the seasons. Because months and years vary in length, conversions involving them are inherently approximate.

Common time conversions

One hour expressed in other units of time
Unit	1 hour equals
Millisecond (ms)	3,600,000
Second (s)	3,600
Minute (min)	60
Day (d)	0.041666667
Week (wk)	0.005952381
Month (average) (mo)	0.0013689535
Year (365.2425 d) (yr)	0.00011407946

Everyday uses

Project, study and revision planning
Scheduling across time zones
Physics, astronomy and computing
Sports and pace calculations
Billing and timesheet work

Calendar units are irregular: months range from 28 to 31 days, and leap years add a day. Conversions involving months or years are approximate.

Frequently asked questions

How many seconds are in a day?

86,400 in the standard 24-hour day, although the true solar day varies by a fraction of a second.

How many weeks are in a year?

52 weeks and one day — or two days in a leap year.

What is the difference between a Julian and a Gregorian year?

A Julian year is exactly 365.25 days, while the Gregorian calendar averages 365.2425 days.

Why do milliseconds matter?

They are a common threshold in computing and in human reaction-time research, where a few hundred milliseconds is significant.

More worked examples

90 minutes is 1.5 hours, or 5,400 seconds.
One day contains 86,400 seconds.
Two and a half hours is 2 hours 30 minutes, not 2 hours 50 minutes.
The Gregorian calendar averages 365.2425 days per year.

Quick reference

Common time periods and their equivalents
Period	Equivalent
1 minute	60 seconds
1 hour	60 minutes, 3,600 seconds
1 day	24 hours, 86,400 seconds
1 week	7 days, 604,800 seconds
1 mean year	365.2425 days
1 millisecond	0.001 seconds
1 microsecond	0.000001 seconds

Common mistakes to avoid

Reading decimal hours as hours and minutes. A value of 1.5 hours is 1 hour 30 minutes, not 1 hour 50 minutes.
Assuming every month has 30 days when totalling long periods, which drifts by a day or two each quarter.
Rounding seconds away when adding many intervals, which compounds into minutes over time.
Forgetting that a decimal day figure needs its fraction multiplied by 24 to give hours.

Further questions

How do I convert decimal hours into hours and minutes?

Keep the whole number as hours, then multiply the decimal part by 60 to get minutes. So 2.75 hours is 2 hours 45 minutes.

Why is a year 365.2425 days?

That is the average length of a Gregorian calendar year, which uses leap years to stay aligned with the seasons.

Is a day exactly 24 hours?

Not quite. The solar day varies slightly through the year, and a sidereal day, measured against the stars, is about 23 hours 56 minutes.

Sources and standards

The second is defined by the caesium hyperfine transition frequency. Civil timekeeping adds leap seconds to stay aligned with the Earth's rotation, which is why NIST and the BIPM both publish the current offset between atomic and astronomical time.