Fortnight to Shake Converter

Convert fortnights to shakes with our free online time converter.

Quick Answer

1 Fortnight = 1.209600e+14 shakes

Formula: Fortnight × conversion factor = Shake

Use the calculator below for instant, accurate conversions.

Our Accuracy Guarantee

All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.

Last verified: December 2025Reviewed by: Sam Mathew, Software Engineer

Fortnight to Shake Calculator

How to Use the Fortnight to Shake Calculator:

  1. Enter the value you want to convert in the 'From' field (Fortnight).
  2. The converted value in Shake will appear automatically in the 'To' field.
  3. Use the dropdown menus to select different units within the Time category.
  4. Click the swap button (⇌) to reverse the conversion direction.
Share:

How to Convert Fortnight to Shake: Step-by-Step Guide

Converting Fortnight to Shake involves multiplying the value by a specific conversion factor, as shown in the formula below.

Formula:

1 Fortnight = 1.2096e+14 shakes

Example Calculation:

Convert 60 fortnights: 60 × 1.2096e+14 = 7.2576e+15 shakes

Disclaimer: For Reference Only

These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.

Not for professional use. Results should be verified before use in any critical application. View our Terms of Service for more information.

What is a Fortnight and a Shake?

The Fourteen-Day Period

A fortnight is precisely 14 consecutive days, representing two full weeks.

Exact equivalents:

  • 14 days (by definition)
  • 336 hours (14 days × 24 hours)
  • 20,160 minutes (336 hours × 60 minutes)
  • 1,209,600 seconds (20,160 minutes × 60 seconds)

Not variable: Unlike months (28-31 days), the fortnight is always exactly 14 days, making it a consistent scheduling unit.

Etymology: Counting by Nights

The word "fortnight" combines:

  • "Fourteen" (the number 14)
  • "Night" (from Old English "niht")

Old English origin: "Fēowertīene niht" = "fourteen nights"

Why nights, not days? Ancient Germanic peoples observed the lunar cycle for timekeeping. The moon's visibility at night made nights more prominent for tracking time than daylight periods. This night-counting tradition appears in related Germanic languages:

  • Dutch: "veertien dagen" (fourteen days) — shifted from nights to days
  • German: "vierzehn Tage" (fourteen days) — also shifted to days
  • Icelandic: "fj

ógur dagar" (fourteen days)

English uniquely preserves the "night" etymology, though modern usage refers to the complete 14-day period regardless of time of day.

Relationship to Weeks and Months

Two weeks: A fortnight is exactly half a lunar month (~29.5 days ÷ 2 ≈ 14.75 days), though slightly shorter. This makes it a natural intermediate period between the week (7 days) and the month.

Calendar months:

  • 26-27 fortnights per year (365.25 days ÷ 14 = 26.09 fortnights)
  • ~2.17 fortnights per month (30.44 days ÷ 14)

The fortnight provides a convenient subdivision smaller than a month but larger than a week, useful for payroll, rent, and recurring obligations.

A Shake is an informal unit of time equal to 10 nanoseconds (10 ns), or 10⁻⁸ seconds. It is primarily used in nuclear physics and astrophysics to measure the timing of events in nuclear reactions and related phenomena.

Note: The Fortnight is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Shake belongs to the imperial/US customary system.

History of the Fortnight and Shake

Ancient Germanic Night-Counting (Pre-9th Century)

Lunar observation: Before written calendars, Germanic tribes tracked time using the moon's phases. The new moon to full moon cycle (approximately 14-15 days) created natural fortnight-length periods.

Night prominence:

  • Full moons illuminated nights, making them memorable markers
  • Daylight periods blurred together without distinct markers
  • Nights were counted: "three nights hence," "fourteen nights from now"

This system influenced Old Norse, Old English, and other Germanic languages.

Old English Documentation (9th-11th Centuries)

Anglo-Saxon Chronicle (circa 890 CE): The earliest written English historical record uses "fēowertīene niht" to describe fourteen-day periods in battle accounts and political events.

Beowulf (8th-11th century): The epic poem references time periods measured in nights, including fortnight-length durations for journeys and feasts.

Legal codes: Anglo-Saxon law codes (Aethelberht, Alfred the Great) used fortnights for legal waiting periods and court summons.

Middle English Evolution (12th-15th Centuries)

Spelling variations:

  • "Fourtenyght" (14th century)
  • "Fourtenight" (15th century)
  • "Fourteenyght"
  • Gradual simplification toward "fortnight"

Chaucer's Canterbury Tales (1387-1400): Geoffrey Chaucer used fortnight references, solidifying the term in literary English: "And eek me thynketh in my remembraunce, / I have herd telle of a fortnyght or thre"

Medieval commerce: Markets and fairs often operated on fortnight cycles, with merchants returning to towns every two weeks.

Early Modern English (16th-17th Centuries)

Standardization: By the 1500s, "fortnight" became the dominant spelling and pronunciation.

Shakespeare's usage (1590s-1610s): William Shakespeare used "fortnight" frequently across his plays:

  • The Tempest (1611): "I'll deliver all; And promise you calm seas, auspicious gales, And sail so expeditious that shall catch Your royal fleet far off. My Araby, chick! That is thy charge: then to the elements Be free, and fare thou well! Please you, draw near." (References to travel time in fortnights)
  • The Two Gentlemen of Verona
  • Much Ado About Nothing

Shakespeare's widespread influence ensured "fortnight" became standard educated English.

British Empire and Commonwealth Spread (17th-19th Centuries)

Colonial administration: British colonial governments used fortnightly reporting cycles, payment schedules, and administrative periods.

Spread to:

  • Australia (colonized 1788 onward)
  • New Zealand (colonized 1840 onward)
  • India (British Raj, 18th-20th centuries)
  • Canada (though later influenced by American "two weeks")
  • South Africa, Caribbean, East Africa

Embedded in law: Colonial legal codes, rental agreements, and labor contracts specified fortnightly terms, creating lasting institutional usage.

Industrial Revolution and Labor Movements (19th Century)

Fortnightly wages: British factories and mills established fortnightly pay cycles during the Industrial Revolution (1760-1840):

  • Workers received wages every two weeks
  • Easier for employers to manage than weekly payroll
  • Allowed workers to budget for monthly rent

Labor union influence: Trade unions negotiated fortnightly pay as standard, spreading throughout the British Empire.

Australian adoption: Australian colonies (becoming a federation in 1901) adopted fortnightly wages widely. Today, Australia has the world's highest fortnight usage, with most wages, rent, and bills calculated fortnightly.

American Divergence (20th Century)

"Two weeks" replaces "fortnight": American English gradually abandoned "fortnight" during the 20th century in favor of "two weeks."

Reasons:

  • Simplicity: "Two weeks" is more transparent to non-native speakers
  • Bi-weekly confusion: "Bi-weekly" can mean either twice per week or once every two weeks, causing ambiguity
  • Cultural shift: American preference for straightforward terminology

Result: By the 21st century, "fortnight" sounds archaic or quaint to most Americans.

Modern Commonwealth Usage (1900s-Present)

United Kingdom: Fortnightly payroll, magazine publications ("published fortnightly"), TV schedules (reality shows with "fortnightly evictions").

Australia and New Zealand:

  • Dominant time unit: Wages almost universally paid fortnightly
  • Rental agreements: Rent calculated per fortnight (not per week or month)
  • Government benefits: Welfare payments issued fortnightly

Cultural persistence: Despite global influence of American English, fortnight remains deeply embedded in Commonwealth life, appearing daily in conversation, media, and official documents.

The term "Shake" originated during the Manhattan Project, the World War II effort to develop the first nuclear weapons. Nuclear chain reactions happen extremely quickly, and physicists needed a convenient, short unit of time to discuss the timing of events within these reactions. Ten nanoseconds was chosen as a practical order of magnitude for many processes involved. The name itself is informal, reputedly derived from the expression "two shakes of a lamb's tail," implying a very short duration.

Common Uses and Applications: fortnights vs shakes

Explore the typical applications for both Fortnight (imperial/US) and Shake (imperial/US) to understand their common contexts.

Common Uses for fortnights

1. British and Commonwealth Payroll

Fortnightly pay period: The most widespread use of fortnight is in employment contracts specifying pay every 14 days.

Advantages:

  • 26 pay periods per year (simpler arithmetic than 52 weekly periods)
  • Budget-friendly: Easier to align with monthly bills
  • Payroll efficiency: Reduces administrative burden compared to weekly pay

Typical schedule: Employees paid on alternating Fridays, creating a predictable two-week cycle.

2. Australian Rental Agreements

Rent calculation: Australian rental market uniquely quotes rent per fortnight rather than per week or per month.

Conversion formulas:

  • Fortnight to month: Fortnight rent × 26 ÷ 12
  • Month to fortnight: Month rent × 12 ÷ 26

Example:

  • $700/fortnight = $700 × 26 ÷ 12 = $1,516.67/month

3. Scheduling and Planning

Recurring events: "The committee meets fortnightly" = every two weeks

Vacation planning: "I'm taking a fortnight off" = two-week vacation

Project timelines: "Deliver progress reports every fortnight"

4. Literary and Formal Writing

British literature: Historical novels and formal writing use "fortnight" for period flavor.

Legal documents: UK contracts may specify "a fortnight's notice" for resignations or terminations.

5. Sports and Competition Schedules

Tournament cycles: Some sports competitions use fortnightly rounds.

Training schedules: Athletes may follow fortnight-based training cycles (two weeks of intensive training followed by recovery).

6. Historical and Cultural Context

Period dramas: Films and TV set in Britain use "fortnight" for authenticity.

Example dialogue: "The Duke will return in a fortnight."

When to Use shakes

The Shake is almost exclusively used in specific technical fields:

  • Nuclear Physics: Measuring the time intervals between successive neutron generations in a nuclear chain reaction.
  • Astrophysics: Discussing timescales relevant to certain high-energy astrophysical events.
  • Particle Physics: Occasionally used in experiments involving very short-lived particles or interactions.
  • Laser Physics: Sometimes used in contexts involving very short laser pulses.

It is not used for everyday time measurements.

Additional Unit Information

About Fortnight (fn)

How many days are in a fortnight?

Exactly 14 days.

A fortnight is always 14 consecutive days, equivalent to two full weeks (7 days × 2).

Time equivalents:

  • 336 hours
  • 20,160 minutes
  • 1,209,600 seconds

How many weeks make a fortnight?

Exactly 2 weeks = 1 fortnight.

This is the definition of the term: "fortnight" literally means "fourteen nights" (two weeks).

Where does the word "fortnight" come from?

From Old English "fēowertīene niht" (fourteen nights).

Etymology:

  • "Fēowertīene" = fourteen
  • "Niht" = night

Historical context: Ancient Germanic peoples counted time by nights rather than days, observing lunar cycles. The fortnight represents approximately half a lunar month (~29.5 days ÷ 2).

Evolution: Old English "fēowertīene niht" → Middle English "fourtenyght" → Modern English "fortnight"

Is "fortnight" commonly used everywhere?

No—usage is heavily geographic.

Common in:

  • United Kingdom (standard term)
  • Ireland (standard term)
  • Australia (most common time unit for pay/rent)
  • New Zealand (standard term)
  • Other Commonwealth nations (varying frequency)

Rare in:

  • United States (sounds archaic; "two weeks" preferred)
  • Canada (mixed usage; more American influence)

Result: "Fortnight" is standard British/Commonwealth English but virtually unused in American English.

What's the difference between fortnight and bi-weekly?

Fortnight = unambiguous 14-day period

Bi-weekly = ambiguous; two possible meanings:

  1. Every two weeks (synonymous with fortnightly)
  2. Twice per week

Recommendation: Use "fortnight" or "every two weeks" to avoid confusion. "Bi-weekly" can mislead readers.

Example:

  • Ambiguous: "Bi-weekly payroll" (twice per week or every two weeks?)
  • Clear: "Fortnightly payroll" (unambiguous: every 14 days)

How many fortnights are in a year?

Approximately 26.09 fortnights per year.

Calculation: 365.25 days (average year with leap years) ÷ 14 days = 26.089 fortnights

Payroll standard: Employers use 26 pay periods for fortnightly wages, slightly underestimating the true annual length (creates an extra day or two per year).

How do I convert monthly rent to fortnightly rent?

Formula: Fortnight rent = Monthly rent × 12 ÷ 26

Example:

  • Monthly rent: $1,500
  • $1,500 × 12 ÷ 26 = $692.31 per fortnight

Reverse (fortnight to month): Monthly rent = Fortnight rent × 26 ÷ 12

Example:

  • Fortnight rent: $700
  • $700 × 26 ÷ 12 = $1,516.67 per month

Is a fortnight half a month?

Approximately, but not exactly.

Fortnight: 14 days (fixed)

Half month: Varies by month

  • February: 14 days (coincidentally equal!)
  • January, March, May, July, August, October, December: 15.5 days
  • April, June, September, November: 15 days

Average half month: 30.44 ÷ 2 = 15.22 days (8.7% longer than fortnight)

Conclusion: Fortnight ≈ half month, but they're distinct concepts.

Why do Australians use fortnights so much?

Historical and practical reasons:

1. British colonial influence: Australia inherited British administrative and commercial systems, including fortnightly wage cycles.

2. Payroll alignment: Fortnightly wages became standard, so rent, bills, and budgeting adapted to match pay cycles.

3. Mathematical convenience: 26 fortnights per year simplifies annual calculations compared to 52 weeks.

4. Cultural entrenchment: Generations of Australians have grown up with fortnightly systems, making it the natural default.

Result: Australia likely uses "fortnight" more frequently than any other nation, including the UK.

Do Americans understand "fortnight"?

Most recognize it, but few use it.

Recognition:

  • Americans encounter "fortnight" in British literature, period dramas, and historical contexts
  • Educated Americans know it means "two weeks"

Usage:

  • Virtually never used in everyday American speech
  • Sounds archaic, old-fashioned, or excessively formal

Recommendation: When addressing American audiences, use "two weeks" instead of "fortnight" to ensure clarity.

About Shake (shake)

How long is a Shake in seconds?

One Shake is equal to 10 nanoseconds (10 ns), which is 10⁻⁸ seconds, or 0.00000001 seconds.

Where did the name "Shake" come from?

The name is an informal term coined during the Manhattan Project. It's believed to be a humorous reference to the phrase "in two shakes of a lamb's tail," signifying a very brief period, appropriate for the rapid events in nuclear reactions.

Is the Shake an SI unit?

No, the Shake is not part of the International System of Units (SI). The standard SI unit for time is the second (s). The Shake is a specialized, informal unit used within specific scientific communities for convenience.

Conversion Table: Fortnight to Shake

Fortnight (fn)Shake (shake)
0.560,480,000,000,000
1120,960,000,000,000
1.5181,440,000,000,000
2241,920,000,000,000
5604,800,000,000,000
101,209,600,000,000,000
253,024,000,000,000,000
506,048,000,000,000,000
10012,096,000,000,000,000
25030,240,000,000,000,000
50060,480,000,000,000,000
1,000120,960,000,000,000,000

People Also Ask

How do I convert Fortnight to Shake?

To convert Fortnight to Shake, enter the value in Fortnight in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our time converter page to convert between other units in this category.

Learn more →

What is the conversion factor from Fortnight to Shake?

The conversion factor depends on the specific relationship between Fortnight and Shake. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.

Can I convert Shake back to Fortnight?

Yes! You can easily convert Shake back to Fortnight by using the swap button (⇌) in the calculator above, or by visiting our Shake to Fortnight converter page. You can also explore other time conversions on our category page.

Learn more →

What are common uses for Fortnight and Shake?

Fortnight and Shake are both standard units used in time measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our time converter for more conversion options.

For more time conversion questions, visit our FAQ page or explore our conversion guides.

All Time Conversions

Second to MinuteSecond to HourSecond to DaySecond to WeekSecond to MonthSecond to YearSecond to MillisecondSecond to MicrosecondSecond to NanosecondSecond to DecadeSecond to CenturySecond to MillenniumSecond to FortnightSecond to Planck TimeSecond to ShakeSecond to Sidereal DaySecond to Sidereal YearMinute to SecondMinute to HourMinute to DayMinute to WeekMinute to MonthMinute to YearMinute to MillisecondMinute to MicrosecondMinute to NanosecondMinute to DecadeMinute to CenturyMinute to MillenniumMinute to FortnightMinute to Planck TimeMinute to ShakeMinute to Sidereal DayMinute to Sidereal YearHour to SecondHour to MinuteHour to DayHour to WeekHour to MonthHour to YearHour to MillisecondHour to MicrosecondHour to NanosecondHour to DecadeHour to CenturyHour to MillenniumHour to FortnightHour to Planck TimeHour to ShakeHour to Sidereal DayHour to Sidereal YearDay to SecondDay to MinuteDay to HourDay to WeekDay to MonthDay to YearDay to MillisecondDay to MicrosecondDay to NanosecondDay to DecadeDay to CenturyDay to MillenniumDay to FortnightDay to Planck TimeDay to ShakeDay to Sidereal DayDay to Sidereal YearWeek to SecondWeek to MinuteWeek to HourWeek to DayWeek to MonthWeek to YearWeek to MillisecondWeek to MicrosecondWeek to NanosecondWeek to DecadeWeek to CenturyWeek to MillenniumWeek to FortnightWeek to Planck TimeWeek to ShakeWeek to Sidereal DayWeek to Sidereal YearMonth to SecondMonth to MinuteMonth to HourMonth to DayMonth to WeekMonth to YearMonth to MillisecondMonth to MicrosecondMonth to NanosecondMonth to DecadeMonth to CenturyMonth to MillenniumMonth to FortnightMonth to Planck TimeMonth to ShakeMonth to Sidereal DayMonth to Sidereal YearYear to SecondYear to MinuteYear to HourYear to DayYear to WeekYear to MonthYear to MillisecondYear to MicrosecondYear to NanosecondYear to DecadeYear to CenturyYear to MillenniumYear to FortnightYear to Planck TimeYear to ShakeYear to Sidereal DayYear to Sidereal YearMillisecond to Second

Verified Against Authority Standards

All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.

NIST Time and Frequency

National Institute of Standards and TechnologyOfficial time standards and definitions

BIPM Second Definition

Bureau International des Poids et MesuresDefinition of the SI base unit for time

Last verified: December 3, 2025