Calculation methods in depth
This is the technical companion to how prayer times are calculated. That page explains the ideas in plain language; this one gives the exact parameters behind every method and a side-by-side table of how they differ. All of it runs on your device through Adhan.js; no service is called.
What a method actually specifies
A “calculation method” is a small bundle of parameters. Only the first genuinely varies between authorities; the rest are shared or come from your school.
- Fajr angle - the sun's depression below the horizon at which dawn begins.
- Isha angle - the depression at which night begins - or, for a few authorities, a fixed interval (e.g. 90 minutes) after Maghrib instead of an angle.
- Maghrib angle - normally 0° (true sunset). Only the Shia (Jafari) convention delays it to a small depression.
- Asr shadow factor - 1 (standard) or 2 (Ḥanafī). This comes from your madhhab setting, not the method.
- High-latitude rule - how to behave when, at far-north or far-south latitudes, the sun never reaches the Fajr or Isha angle.
Fajr and Isha: the depression angle
Dawn and nightfall are twilight events, so they are defined by how far the sun sits below the horizon. A larger angle means a darker sky, so a larger Fajr angle makes Fajr earlier, and a larger Isha angle makes Isha later. The full spread across mainstream methods is roughly 12° to 20°. For a location and date, Adhan.js solves the time at which the sun's centre reaches that depression. This is the only parameter authorities genuinely disagree on.
The two special cases
Fixed-interval Isha
Umm al-Qura (Saudi Arabia) and Qatar do not use an Isha angle at all. They define Isha as a fixed 90 minutes after Maghrib (Umm al-Qura extends this to 120 minutes during Ramadan). This is a deliberate rule, not an approximation: it makes Isha's clock time steadier through the year than an angle would.
The Shia (Jafari) parameters
The Tehran convention (Institute of Geophysics, University of Tehran) reflects Jafari fiqh: Fajr 17.7°, Isha 14°, and crucially a Maghrib angle of 4.5° - Maghrib begins not at visible sunset but once the sun is 4.5° below the horizon (the disappearance of the eastern redness). Its Islamic midnight is the midpoint between sunset and Fajr, not sunset and sunrise.
Asr: set by madhhab, not method
Asr begins when an object's shadow has grown by a set multiple of its own length. The standard view (Shāfiʿī, Mālikī, Ḥanbalī) uses a factor of 1; the Ḥanafī view uses 2, which pushes Asr materially later (by up to an hour). Because this is a shadow rule, it is driven by your school setting and applies on top of whichever calculation method you choose.
Maghrib, sunrise, midnight
Sunrise and Maghrib (except in the Shia convention above) are the plain astronomical sunrise and sunset - identical for every method, and, together with midday, the only events the “can I pray now” verdict depends on. Islamic midnight, where a method needs it, is the midpoint of the night; the Jafari convention measures the night sunset-to-Fajr rather than sunset-to-sunrise.
High latitudes
Far from the equator in summer the sun may never sink to 18° below the horizon, so a pure angle yields no Fajr or Isha at all. Conventions handle this with a high-latitude rule - commonly the middle of the night, the one-seventh of the night, or an angle-based portion - and the Moonsighting Committee convention adds a seasonal adjustment tuned for these latitudes. This app is deliberately conservative: when the astronomy cannot resolve an event for your date and place, it says so and shows no verdict rather than inventing a time. Residents of such latitudes should follow local scholarly guidance. See the methodology.
How each method differs
Every method below is computed on your device. Angles are the sun's depression at Fajr / Isha; “90 min” means Isha is a fixed interval after Maghrib. Asr shown is the default that pairs with the region; you can always switch schools. ACJU and Kemenag are fitted to those authorities' own tables, the rest are published presets.
| Method | Fajr | Isha | Asr | Distinctive rule | Typical region |
|---|---|---|---|---|---|
| Muslim World League | 18° | 17° | Standard | The common baseline | Europe, much of Africa, worldwide default |
| ISNA (North America) | 15° | 15° | Standard | Shallowest angles - latest Fajr, earliest Isha | USA, Canada |
| Egyptian | 19.5° | 17.5° | Standard | - | Egypt |
| Umm al-Qura | 18.5° | 90 min after Maghrib | Standard | Fixed Isha interval (120 min in Ramadan) | Saudi Arabia |
| Karachi | 18° | 18° | Ḥanafī | Symmetric 18/18 | Pakistan, India, Bangladesh, Afghanistan |
| Tehran | 17.7° | 14° | Standard | Maghrib at 4.5° below horizon; Jafari midnight | Iran, Shia communities |
| Dubai | 18.2° | 18.2° | Standard | - | UAE |
| Kuwait | 18° | 17.5° | Standard | - | Kuwait |
| Qatar | 18° | 90 min after Maghrib | Standard | Fixed Isha interval | Qatar |
| MUIS (Singapore) | 20° | 18° | Standard | Deep Fajr angle | Singapore, Malaysia, Brunei |
| Diyanet (Turkey) | 18° | 17° | Standard | Official tables add a temkin margin | Turkey, DITIB mosques |
| UOIF (France) | 12° | 12° | Standard | Shallowest of all - much later Fajr, earlier Isha | France |
| SAMR (Russia) | 16° | 15° | Ḥanafī | - | Russia |
| Moonsighting Committee | 18° | 18° | Standard | Seasonal high-latitude adjustment | UK, Ireland, Nordics |
| ACJU (Sri Lanka) | 20° | 18° | Standard | Fitted to ACJU's tables; served from their extracted timetable | Sri Lanka |
| Kemenag (Indonesia) | 20° | 18° | Standard | Authority adds ~2 min iḥtiyāṭ (safety margin) | Indonesia |
The practical takeaway: the extremes are UOIF (12°) at one end and MUIS / ACJU / Kemenag (20°) at the other, an 8° spread that can move Fajr by well over half an hour at a given place. Everything else the verdict relies on - sunrise, midday, sunset - is identical across every row. For the country-by-country mapping of which authority uses which of these, see how prayer times are calculated.