Months to Fortnights (mo to fortnight)

1 month equals 2.1740625 fortnights exactly.

1 month = 2.1740625 fortnights

How to convert months to fortnights

To convert months to fortnights, multiply the number of months by 2.1740625. This factor is exact. To go the other way, multiply fortnights by 0.4599683772 (rounded).

fortnights = months × 2.1740625

Example: 10 months = 21.740625 fortnights.

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

Month (mo)

CalendarCurrent unit

One twelfth of an average Gregorian year: 30.436875 days. Calendar months actually range from 28 to 31 days.

Month and Moon are cognates, and the unit began as the Moon's cycle of phases, about 29.53 days from one new moon to the next. The trouble is that 12 of these fall short of a solar year, so calendars have had to choose. The Islamic calendar stays purely lunar, so its year is about 11 days shorter than the solar year, while the Hebrew calendar is lunisolar, using a 19-year cycle with an extra month. Even the start of a lunar month is still debated between observing the crescent and calculating it.

Gregorian months are a compromise that drifted far from the Moon. Their lengths run from 28 to 31 days, and this site uses their mean of 30.436875 days, one twelfth of the average year. The names also keep Roman history: September to December preserve the Latin numerals for seven to ten, since they were originally the seventh to tenth months, and Quintilis and Sextilis were renamed for Julius Caesar and Augustus. When a contract says month, check whether it means a calendar month or thirty days.

1 month = 2,629,746 seconds (exactly).

Sources: Wikipedia: Month; Wikipedia: Lunar calendar

Fortnight (fortnight)

Imperial (British)Traditional unit (still used in some regions)

Fourteen days; short for 'fourteen nights'. Common in British English.

English inherited fortnight from Old English feowertyne niht, fourteen nights, a reminder that early Germanic peoples reckoned time by nights rather than days. It means exactly two weeks, or 14 days, which is 1,209,600 seconds. Many languages lack a single word for the span, so speakers say two weeks or fourteen days instead.

Other languages tend to count inclusively, as in Welsh pythefnos, meaning fifteen nights, matching wythnos for a week, or Spanish quincena and French quinzaine, which all point to fifteen. The Hindu calendar uses paksa for a half of a lunar month. In astronomy a lunar fortnight is half a synodic month, about 14.77 days, which is slightly longer than the calendar fortnight. Neighbouring units are the week, at half a fortnight, and the month, which holds roughly two of them.

1 fortnight = 1,209,600 seconds (exactly).

Sources: Wikipedia: Fortnight

Related conversions

See all time units.