Days to Milliseconds (d to ms)
1 day equals 86,400,000 milliseconds exactly.
How to convert days to milliseconds
To convert days to milliseconds, multiply the number of days by 86,400,000. This factor is exact. To go the other way, multiply milliseconds by 1.157407407×10⁻⁸ (rounded).
milliseconds = days × 86,400,000
Example: 10 days = 864,000,000 milliseconds.
Months and years are not constant. This site uses the average Gregorian year of 365.2425 days, so one 'year' converts to 365.2425 days, not 365; use 'common year' for exactly 365 days.
About these units
Day (d)
24 hours or 86,400 seconds. The mean solar day; the actual rotation of the Earth is about 4 minutes shorter (see sidereal day).
Old English dæg is the root of our day, with close cousins in German Tag, Dutch dag and Icelandic dagur, all descending from Proto-Germanic dagaz. It is the oldest unit here, because the cycle of light and dark needs no instrument. Yet the day we count is a constructed average: the actual interval from one noon to the next varies through the year by up to about 7.9 seconds, because Earth's orbit is elliptical and its axis is tilted.
Astronomers smooth this out with a fictitious mean Sun, giving the mean solar day, and the day in the SI sense is fixed at exactly 86,400 seconds. Reality has drifted slightly: the mean solar day has recently averaged about 86,400.002 seconds, and tidal drag from the Moon is lengthening it by about 2 milliseconds per century. That is why 27 leap seconds were added to UTC between 1972 and 2022. One rotation measured against the distant stars is shorter, about 23 hours 56 minutes 4.09 seconds, and a year contains one more of these sidereal days than solar days.
1 day = 86,400 seconds (exactly).
Sources: Wikipedia: Day; BIPM: SI Brochure, 9th edition
Millisecond (ms)
One thousandth of a second. Used for computer response times and sports timing.
Milliseconds sit on the border between what people perceive and what instruments must be built to catch. Nobody feels a single one: a human blink lasts roughly 100 to 400 of them, and the average resting heart cycle is about 860. The prefix milli- makes the unit exactly one thousandth of a second, so it is a handy yardstick for events a little too quick to notice but slow enough for a stopwatch-style instrument to capture.
A millisecond is one thousandth of a second, and the scale references are easy to picture. Light in a vacuum covers about 300 km in 1 ms, and sound in air covers about 34 cm. A film frame at 24 frames per second lasts about 41.7 ms, one cycle of 60 Hz mains power lasts about 16.7 ms, and a camera shutter set to 1/125 s is open for about 8 ms. Online gamers watch network latency in milliseconds, with typical broadband figures of 5 to 80 ms, and telephone engineers recommend keeping one-way delay under about 150 ms before conversation starts to feel awkward.
1 millisecond = 0.001 seconds (exactly).
Sources: Wikipedia: Millisecond; BIPM: SI Brochure, 9th edition
Related conversions
- Milliseconds to days (reverse)
- Days to seconds
- Days to minutes
- Days to hours
- Days to weeks
- Days to months
- Days to years
- Days to microseconds
- Days to nanoseconds
- Days to decades
- Days to centuries
- Days to millennia
- Days to picoseconds
- Seconds to milliseconds
- Minutes to milliseconds
- Hours to milliseconds
- Weeks to milliseconds
- Months to milliseconds
- Years to milliseconds
- Microseconds to milliseconds
- Nanoseconds to milliseconds
- Decades to milliseconds
- Centuries to milliseconds
- Millennia to milliseconds
See all time units.