Free · Unit conversions

Milliseconds, Seconds & Duration Unit Converter

Convert fixed durations between milliseconds, microseconds, seconds, minutes, hours, days and average longer units.

  • Formula & worked example
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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

86,400,000 milliseconds equal 86,400 seconds, 1,440 minutes, 24 hours or one fixed 24-hour day. The same duration is 86,400,000,000 microseconds.

Seconds = milliseconds ÷ 1000; minutes = seconds ÷ 60; hours = seconds ÷ 3600; fixed days = seconds ÷ 86400

Worked example

Enter these known values and leave the other values blank.

Time in milliseconds
86400000 ms
Time in seconds
86400 sec
Time in minutes
1440 min
Time in hours
24 hrs
Time in days
1 days
Time in other units
86400000000 µs

Assumptions and limitations

  • A day means exactly 24 hours. The optional year is a Julian year of 365.25 days; a month is one twelfth of that year, or 30.4375 days. These fixed units do not calculate elapsed time between calendar dates.
  • Time zones, daylight-saving transitions and leap seconds are outside the model. Signed durations keep their sign across units. For combined hours/minutes/seconds, separate the components with colons.

Common questions

How many milliseconds are in a second?

There are exactly 1,000 milliseconds in one second and 1,000 microseconds in one millisecond.

Why does the month option use an average?

Calendar months have different lengths. A fixed unit conversion needs one factor, so this model uses a twelfth of a 365.25-day year.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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