One sidereal day is exactly 8.61640905e+10 microseconds, so converting sidereal days to microseconds is a single multiplication. Enter any figure and the result appears as you type — the arithmetic runs in your browser, so nothing is sent anywhere.
One millionth of a second, the scale of memory latency. One rotation of Earth relative to the stars: 23 h 56 min 4.09 s, about four minutes short of a solar day.
Months and years are not fixed. This page uses the average Gregorian month of 30.44 days and the Julian year of 365.25 days, which is right for durations and wrong for calendars: three months from 31 January is not 91.31 days in any useful sense. Use a date calculator for calendar arithmetic. Two tables follow: rounded steps for quick lookup, and a set of real reference quantities converted into microseconds, which is usually more useful than the bare number.
The formula
sidereal days- The amount you are converting, in sidereal days
86,164,090,500- The exact number of microseconds in one sidereal day
microseconds- The converted result
How it works, step by step
- Enter the value in sidereal days.
- It is multiplied by 86,164,090,500, the exact factor between the two units.
- The answer is shown in microseconds, with the reverse conversion beneath it.
- Check the reference table if you want a figure of comparable size.
Worked examples
A working day: 0.334 sd in microseconds
A working day comes to about 0.334 sd. Multiplying by the factor: 0.334 × 8.61641e+10 = 2.87788e+10 µs. Dividing the answer back by 8.61641e+10 returns the figure you started with, which is the quickest way to check you have the factor the right way up.
A pop song: 0.00244 sd in microseconds
Take a pop song, roughly 0.00244 sd. The conversion is a single multiplication — 0.00244 × 8.61641e+10 — giving 2.1024e+08 µs. Because the relationship is proportional, doubling the input doubles the answer to 4.20481e+08 µs.
How to read your score
Frequently asked questions
How many microseconds are in one sidereal day?
Exactly 86,164,090,500. Every figure on this page is that one number multiplied by your input, so the only rounding is at the display step.
What is the formula to convert sidereal days to microseconds?
microseconds = sidereal days × 86,164,090,500. Reversed, sidereal days = microseconds ÷ 86,164,090,500, which is the same as multiplying by 1.16057628439e-11.
Which is the bigger unit, the sidereal day or the microsecond?
The sidereal day. One sidereal day equals 8.61641e+10 microseconds.
What does this quantity actually measure?
Both units measure time. That is why a single factor is enough: there is no temperature offset and no material property involved, unlike conversions that cross between different quantities.
What is a sidereal day?
One rotation of Earth relative to the stars: 23 h 56 min 4.09 s, about four minutes short of a solar day.
What is a microsecond?
One millionth of a second, the scale of memory latency.
Why does my answer differ from another converter?
Almost always because the other tool rounded the factor before multiplying. This page keeps full double precision through the calculation and rounds only for display, and it prints the factor it used so you can see where any difference came from.
Is there a quick way to do sd to µs in my head?
Plenty of people do this in their head: multiply by 86000000000.000000 instead of using the exact factor 86164090500.000015. At 100 that shortcut gives 8600000000000.000000 microseconds, off by 16409050000.001953 microseconds or about 0.19%. Fine for a rough estimate, not fine for anything you are cutting to size or dosing.
Sidereal Days to microseconds reference tables
| Sidereal Days | Microseconds |
|---|---|
| 0.5 sd | 4.3082e+10 µs |
| 1 sd | 8.61641e+10 µs |
| 2 sd | 1.72328e+11 µs |
| 3 sd | 2.58492e+11 µs |
| 5 sd | 4.3082e+11 µs |
| 10 sd | 8.61641e+11 µs |
| 20 sd | 1.72328e+12 µs |
| 25 sd | 2.1541e+12 µs |
| 50 sd | 4.3082e+12 µs |
| 75 sd | 6.46231e+12 µs |
| 100 sd | 8.61641e+12 µs |
| 250 sd | 2.1541e+13 µs |
| 500 sd | 4.3082e+13 µs |
| 1000 sd | 8.61641e+13 µs |
| 5000 sd | 4.3082e+14 µs |
Exact factor: 1 sidereal day = 86,164,090,500 microseconds.
| Quantity | sd | µs |
|---|---|---|
| A camera flash | 1.161e-08 sd | 1000 µs |
| A heartbeat | 9.946e-06 sd | 8.57e+05 µs |
| A pop song | 0.002437 sd | 2.1e+08 µs |
| A working day | 0.3342 sd | 2.88e+10 µs |
| A pregnancy | 280.8 sd | 2.419e+13 µs |
| A mortgage term | 8790 sd | 7.574e+14 µs |
Published reference values, converted with the same factor this page uses.