Convert Weeks to Fortnights
Convert Weeks (wk) to Fortnights (fn) instantly and accurately.
Conversion Formula
fn = wk × 0.5
About Weeks
A week (wk) = exactly 7 days = 604,800 s. The 7-day week derives from Babylonian astronomy assigning one of the seven classical celestial bodies to each day - preserved in English (Sun-day, Mon-day, Satur-day) and Romance language day names. It spread globally via Jewish, Christian, and Islamic calendars. ISO 8601 numbers weeks 1-52(53) with Monday as day 1. 365-day years contain 52 weeks + 1 day. 1 wk = 7 d = 604,800 s.
About Fortnights
A fortnight = exactly 14 days = 2 weeks = 1,209,600 s. From Old English 'feowertiene niht' (fourteen nights), reflecting the Germanic custom of counting nights. Common in British, Irish, Australian, and NZ English for pay periods, rental cycles, and parliamentary recesses. The Moon's phase advances ~half a synodic month (≤14.77 days) per fortnight; spring and neap tides also cycle fortnightly. 1 fortnight = 14 d = 1,209,600 s.
Quick Reference Table
| Weeks (wk) | Fortnights (fn) |
|---|---|
| 1 wk | 0.5 fn |
| 2 wk | 1 fn |
| 5 wk | 2.5 fn |
| 10 wk | 5 fn |
| 25 wk | 12.5 fn |
| 50 wk | 25 fn |
| 100 wk | 50 fn |