The Ramadan fast lasts from Fajr to Maghrib. The duration depends on three things: latitude, the time of year Ramadan falls (because the Hijri calendar moves ~11 days earlier each Gregorian year), and the local Fajr/Isha calculation method.
Typical ranges
Around the equator (e.g. Singapore, Kuala Lumpur) the fast is roughly 13 hours year-round. In Mecca, Cairo, and Riyadh it ranges from about 13 to 15 hours. In London, Paris, Berlin the fast can reach 16–19 hours when Ramadan falls in summer, and drop to 11–12 hours when it falls in winter.
Look up your city
Use any QiblaWeb city page (/en/ramadan) to see Suhoor and Iftar timings for the upcoming Ramadan in your city. You can also export a privacy-respecting ICS calendar file to your phone calendar — no notification subscription, no account.
Extreme latitudes
At very high latitudes (e.g. parts of Scandinavia, Alaska) the sun may not set, or may not rise, for extended periods. In such places scholars allow following either the timings of Mecca or the timings of the nearest city with a normal day-night cycle, or applying a "middle of the night" rule. Follow the methodology your local mosque uses.
Source
Calculation methodology summarized from AlAdhan — Prayer calculation methods (retrieved 2026-05-09).