Convert Months to Sidereal Months
Convert Months (mo) to Sidereal Months (sid.mo) instantly and accurately.
Conversion Formula
sid.mo = mo × 1.114019906
About Months
A mean Gregorian calendar month = 365.2425 ÷ 12 = 30.436875 days = 2,629,746 s exactly (averaged over the 400-year cycle with exactly 97 leap years). Individual months have 28-31 days. Loan schedules, subscriptions, and mobile billing reference 'per month', requiring explicit agreement on meaning. ISO 8601 uses 'P1M'. 1 mo = 30.436875 d = 2,629,746 s.
About Sidereal Months
The sidereal month = Moon's orbital period relative to the fixed stars = 27.3217 days = 2,360,591.6 s - the shortest lunar month. It is ~2.21 days shorter than the synodic month (29.53 d) because Earth advances ~27° along its orbit in the same period; the Moon must travel further to re-align with the Sun. Used in GPS orbit design, tidal modelling, and lunar laser ranging. 1 sid.mo = 27.3217 d.
Quick Reference Table
| Months (mo) | Sidereal Months (sid.mo) |
|---|---|
| 1 mo | 1.11402 sid.mo |
| 2 mo | 2.22804 sid.mo |
| 5 mo | 5.5701 sid.mo |
| 10 mo | 11.1402 sid.mo |
| 25 mo | 27.8505 sid.mo |
| 50 mo | 55.701 sid.mo |
| 100 mo | 111.402 sid.mo |