Two ways calculation presets define Isha
Across the ten calculation presets supported by SalahTable (see our methodology), Isha is computed in one of two ways:
- Fixed interval after Maghrib: The Umm al-Qura (Saudi Arabia default) and Qatar presets place Isha exactly 90 minutes after Maghrib. In these presets, the Isha calculation depends on sunset plus a fixed duration rather than a solar depression angle.
- Twilight depression angle: Presets such as ISNA (15°), Muslim World League (17°), Egyptian and Kuwait (17.5°), Karachi and Singapore (18°), Dubai (18.2°) and Moonsighting Committee (18° with seasonal adjustment) compute when the sun sinks to a specified angle below the western horizon, or apply a high-latitude fallback when that angle is not reached.
Note on Ramadan in Umm al-Qura calendars: printed Umm al-Qura schedules in Saudi Arabia often add 30 minutes to the Isha interval during Ramadan (making it 120 minutes after Maghrib). In Adhan 4.4.6 as run on SalahTable, the standard Umm al-Qura preset uses a 90-minute interval year-round so daily comparisons remain uniform across Gregorian dates.
90-minute interval vs twilight angles across four cities (2027)
Because the time required for the sun to sink 15°–18° below the horizon changes with latitude and season, a fixed 90-minute interval is later than an angle-based Isha in low-latitude or winter nights, and earlier than an angle-based Isha in mid-latitude summer nights.
| City / latitude | Date | Maghrib | Umm al-Qura (+90m) | ISNA (15°) | MWL (17°) | Karachi (18°) | +90m vs MWL |
|---|---|---|---|---|---|---|---|
| Makkah 21.4°N · Asia/Riyadh | 21 March 2027 | 6:32 PM | 8:02 PM | 7:33 PM | 7:42 PM | 7:46 PM | +20 min |
| Makkah 21.4°N · Asia/Riyadh | 21 June 2027 | 7:06 PM | 8:36 PM | 8:15 PM | 8:26 PM | 8:31 PM | +10 min |
| Makkah 21.4°N · Asia/Riyadh | 21 September 2027 | 6:18 PM | 7:48 PM | 7:19 PM | 7:28 PM | 7:32 PM | +20 min |
| Makkah 21.4°N · Asia/Riyadh | 21 December 2027 | 5:43 PM | 7:13 PM | 6:49 PM | 6:58 PM | 7:03 PM | +15 min |
| Karachi 24.9°N · Asia/Karachi | 21 March 2027 | 6:43 PM | 8:13 PM | 7:46 PM | 7:55 PM | 7:59 PM | +18 min |
| Karachi 24.9°N · Asia/Karachi | 21 June 2027 | 7:24 PM | 8:54 PM | 8:37 PM | 8:48 PM | 8:53 PM | +6 min |
| Karachi 24.9°N · Asia/Karachi | 21 September 2027 | 6:30 PM | 8:00 PM | 7:33 PM | 7:41 PM | 7:46 PM | +19 min |
| Karachi 24.9°N · Asia/Karachi | 21 December 2027 | 5:48 PM | 7:18 PM | 6:55 PM | 7:05 PM | 7:09 PM | +13 min |
| New York 40.7°N · America/New_York | 21 March 2027 | 7:09 PM | 8:39 PM | 8:25 PM | 8:36 PM | 8:41 PM | +3 min |
| New York 40.7°N · America/New_York | 21 June 2027 | 8:31 PM | 10:01 PM | 10:11 PM | 10:28 PM | 10:37 PM | -27 min |
| New York 40.7°N · America/New_York | 21 September 2027 | 6:55 PM | 8:25 PM | 8:11 PM | 8:21 PM | 8:27 PM | +4 min |
| New York 40.7°N · America/New_York | 21 December 2027 | 4:32 PM | 6:02 PM | 5:54 PM | 6:05 PM | 6:11 PM | -3 min |
| London 51.5°N · Europe/London | 21 March 2027 | 6:15 PM | 7:45 PM | 7:48 PM | 7:55 PM | 7:55 PM | -10 min |
| London 51.5°N · Europe/London | 21 June 2027 | 9:22 PM | 10:52 PM | 10:25 PM | 10:25 PM | 10:25 PM | +27 min |
| London 51.5°N · Europe/London | 21 September 2027 | 7:02 PM | 8:32 PM | 8:35 PM | 8:42 PM | 8:42 PM | -10 min |
| London 51.5°N · Europe/London | 21 December 2027 | 3:53 PM | 5:23 PM | 5:37 PM | 5:51 PM | 5:58 PM | -28 min |
What the seasonal pattern shows
- Near the tropics (Makkah, 21.4° N and Karachi, 24.9° N): Twilight passes relatively quickly throughout the year. The 17° (MWL) and 18° (Karachi) crossings occur roughly 72 to 86 minutes after sunset, so the 90-minute Umm al-Qura preset places Isha 4 to 18 minutes later than MWL in all four seasons.
- Mid-latitude equinoxes and winter (New York, 40.7° N): In March, September and December, 17° twilight takes about 82 to 89 minutes after sunset, close to the 90-minute rule. In June, however, 17° twilight takes 107 minutes, so the 90-minute rule is 17 minutes earlier than MWL.
- High-latitude summer (London, 51.5° N): In June, the sun never reaches 17° or 18° below the horizon in London, and MWL/Karachi switch to a high-latitude approximation, while a 90-minute offset simply adds 1 hour 30 minutes to sunset. See our full-year 2027 method study and high-latitude prayer times page.
When comparing two apps
If two apps agree on Maghrib in Makkah, Riyadh, Doha or another city but disagree on Isha by 10–20 minutes, check whether one is using a 90-minute fixed interval (Umm al-Qura or Qatar) and the other is using a twilight angle (such as MWL 17° or Karachi 18°). You can switch between all ten presets on any city page.