How many weeks are in a fortnight?

Exactly two. Fourteen days divides evenly by seven, so a fortnight is always two whole weeks with no remainder, and it always ends on the same weekday it began. Three fortnights are six weeks, and 26 fortnights are 52 weeks.

How many hours are in a fortnight?

There are 336 hours in a fortnight, since fourteen days multiplied by 24 hours gives 336. That is also 20,160 minutes or 1,209,600 seconds. In regions observing daylight saving time, the elapsed local time across a clock change is 335 or 337 hours.

How do I add a fortnight to a date?

Add fourteen to the day number and subtract the length of the month if the total exceeds it. From 20 January, 20 plus 14 is 34, and January has 31 days, so the answer is 3 February. The weekday never changes, which lets you check the result.

Is a fortnight half a month?

No. A fortnight is fourteen days while the average month is about 30.44 days, so two fortnights fall short of most months by two or three days. Only February in a common year is exactly two fortnights long.

Fortnight to Weeks and Days Conversion

Most unit conversions in the calendar are awkward because months are of unequal length. Converting a fortnight to weeks is the pleasant exception: fourteen days is exactly two weeks, exactly 336 hours, and it never varies by season, year or country. The arithmetic only becomes interesting when you start adding those periods to a real date and crossing the end of a month.

This article gives every conversion you are likely to need, in both directions, and then works through examples of adding and subtracting fourteen-day periods across month boundaries and year ends. To do it on your own dates without counting, the fortnight calculator adds or subtracts any number of periods and returns the exact date and weekday.

How Do You Convert a Fortnight to Weeks and Days?

Multiply by two for weeks and by fourteen for days. One fortnight is two weeks or fourteen days; three fortnights are six weeks or 42 days. Because fourteen is a whole multiple of seven, the conversion is exact and there is never a remainder.

That exactness is the unit's main practical virtue. A month cannot be converted to weeks without a fraction, and a year cannot be converted to months without ignoring their unequal lengths, but a fourteen-day period always resolves cleanly into weeks and days. It also always ends on the same weekday it began, which makes any multiple of it easy to check by eye.

Fortnight to Weeks, Hours and Minutes: The Full Set

These are the conversions worth keeping to hand. Each is exact, with no rounding involved:

Weeks: one fortnight is 2 weeks. Multiply by 2, or halve a week count to go back.
Days: 14 days. Multiply by 14, or divide a day count by 14 to go back.
Hours: 336 hours, since 14 × 24 = 336.
Minutes: 20,160 minutes exactly.
Seconds: 1,209,600 seconds exactly.
Longer runs: two periods are 4 weeks or 28 days; four are 8 weeks or 56 days; twenty-six are 52 weeks or 364 days.

That last line is the one that causes trouble later, because 364 days is not a year. The consequences of the missing day or two are set out in how many fortnights in a year.

Converting Weeks and Days Back to Fortnights

Divide weeks by two and days by fourteen. Six weeks is three fortnights; 56 days is four. Where the number does not divide cleanly, express the remainder in days rather than as a decimal, because a fraction of a fortnight has no useful everyday meaning.

A few common spans converted: ten days is not quite three quarters of a fortnight; a 30-day month is two periods and two days; a 90-day quarter is six periods and six days; 100 days is seven periods and two days. Notice that none of the calendar's own divisions land on a whole number except a common-year February, which is exactly two. That is a structural feature of the calendar rather than a coincidence, and it is why a fourteen-day cycle drifts against monthly commitments such as rent, as explained in fortnightly rent and leases.

Adding Fortnights Across Month Ends

Add fourteen days to the day number, then subtract the length of the month if the result exceeds it. Never treat a fortnight as half a month, and never add it by moving to the same date next month and adjusting, because month lengths differ and the answer will be wrong.

Worked Examples

Take 20 January. Adding 14 gives 34; January has 31 days, so 34 − 31 = 3, and the answer is 3 February. Take 20 February in a common year: 20 + 14 = 34, February has 28 days, so 34 − 28 = 6, giving 6 March. In a leap year the same start date lands on 5 March instead, because February has 29 days that year. A single day of calendar structure moves the result.

Longer spans work the same way. From 30 August, three fortnights is 42 days: one day remains in August, 30 of the remaining 41 fall in September, and the last 11 land in October, so the answer is 11 October. Across a year end, 31 December plus fourteen days is 14 January of the following year. In every case the weekday is unchanged, which gives you a free check on the arithmetic.

Subtracting Fortnights and Working Backwards

Subtract fourteen from the day number and, if the result is zero or negative, add the length of the previous month. Counting backwards from 5 March in a common year gives 5 − 14 = −9, and adding February's 28 days gives 19 February.

Working backwards is the more common need in practice, since it answers questions such as when notice had to be served, or when a countdown should have started. The countdown to any date handles the forward version, reporting the remaining time in whole fourteen-day periods plus a remainder in days, which is usually more legible than a raw day count for anything more than a month away.

Where These Conversions Go Wrong

Three errors account for nearly all mistakes. The first is treating a fortnight as half a month, which is wrong by between zero and three days depending on the month and produces the doubling error that understates annual rent by almost 8 per cent.

The second is inclusive counting. Fourteen days after Monday 1 June is Monday 15 June, but a span described as fourteen days that includes both the first and last day runs only to 14 June. French keeps the older inclusive habit and calls a fortnight quinze jours, fifteen days, for exactly this reason. Where a date matters, write it out rather than trusting the count. The third is assuming that 336 hours always elapse. The period is always fourteen calendar days, but in a region observing daylight saving time the elapsed local time across a clock change is 335 or 337 hours. For definitions and the origin of the unit, see what is a fortnight, or check the current position in the cycle on the current fortnight tracker.

Conclusion

Converting a fortnight to weeks and days is the simplest arithmetic in the calendar: two weeks, fourteen days, 336 hours, 20,160 minutes, with no remainder and no seasonal variation. Adding those periods to a real date only requires one rule, which is to add fourteen to the day number and subtract the month length when it overflows, and one check, which is that the weekday must not change. Watch for inclusive counting, daylight saving, and the temptation to treat fourteen days as half a month. Run any date through the fortnight calculator, or see the rest of the tools on fortnight.now.

Converting Fortnights to Weeks and Days: Every Conversion