Islamic prayer times are defined by natural phenomena: dawn, the sun passing its highest point, the length of shadows, sunset and nightfall. Because these depend on the sun’s position, they can be calculated in advance for any place on Earth using astronomy. The calculation is precise; the differences between timetables come from definitions, chiefly how dark the sky must be for dawn and nightfall, and how long a shadow must be for Asr. This guide explains the astronomy and the conventions neutrally. Questions of religious practice are for scholars and local authorities.
You can see today’s times for your location with our prayer times tool.
The ingredients: latitude, longitude, date and time zone
Every calculation starts from:
- Latitude and longitude: your position on Earth.
- Date: determines the sun’s declination (its angle north or south of the equator, between about −23.44° and +23.44° over the year).
- Equation of time: the difference between clock time and solar time, which varies by up to about 16 minutes through the year.
- Time zone and daylight saving time.
- Sometimes elevation, which slightly affects sunrise and sunset.
From these, standard astronomical formulas give the time when the sun reaches any chosen angle relative to the horizon.
How each prayer time is defined
| Prayer | Astronomical definition (common convention) |
|---|---|
| Fajr | Sun a set number of degrees below the eastern horizon (dawn twilight), e.g. 15°–19.5° |
| Sunrise | Upper edge of the sun appears; calculated at about 0.833° below the horizon to account for refraction and the sun’s radius |
| Dhuhr | Just after solar noon, when the sun crosses the meridian; many timetables add a minute or more as a margin |
| Asr | When an object’s shadow reaches a certain length (see below) |
| Maghrib | Sunset (0.833° below the horizon), sometimes plus a short margin |
| Isha | Sun a set number of degrees below the western horizon, or a fixed interval after Maghrib |
Fajr and Isha: twilight angles
After sunset, the sky darkens gradually as the sun sinks further below the horizon. Astronomers define astronomical twilight as ending when the sun is 18° below the horizon. Islamic calculation methods choose their own angle for when true dawn (Fajr) begins and when evening twilight ends (Isha). A larger angle means an earlier Fajr and a later Isha.
Asr: the shadow ratio
Asr is defined by shadow length, not by an angle. Let the noon shadow of a vertical stick be s₀ (the shortest shadow of the day).
- Standard (Shafi’i, Maliki, Hanbali): Asr begins when shadow = 1 × object height + s₀.
- Hanafi: Asr begins when shadow = 2 × object height + s₀.
The Hanafi Asr is therefore later, often by 30 minutes to over an hour depending on season and latitude. Most apps let you choose between the two.
The main calculation methods
| Method | Fajr angle | Isha | Typically used in |
|---|---|---|---|
| Muslim World League (MWL) | 18° | 17° | Europe, Far East, parts of the Americas |
| Islamic Society of North America (ISNA) | 15° | 15° | USA, Canada |
| Egyptian General Authority of Survey | 19.5° | 17.5° | Egypt, parts of Africa and the Middle East |
| Umm al-Qura University, Makkah | 18.5° | 90 minutes after Maghrib (120 in Ramadan) | Saudi Arabia |
| University of Islamic Sciences, Karachi | 18° | 18° | Pakistan, Bangladesh, India, Afghanistan |
| Diyanet (Presidency of Religious Affairs, Türkiye) | 18° | 17° | Türkiye; times include small fixed safety adjustments |
| Institute of Geophysics, University of Tehran | 17.7° | 14° (Maghrib at 4.5°) | Iran; Shia conventions |
Other regional bodies (in the Gulf states, Malaysia, Indonesia, Singapore, France, Russia and elsewhere) publish their own parameters, and in the UK many mosques follow local timetables or the Moonsighting Committee approach, which uses seasonal adjustments. Libraries such as those behind most prayer apps implement these methods and let you switch between them.
How big is the difference? At mid-latitudes, moving from 15° (ISNA) to 18° (MWL) typically makes Fajr about 15–25 minutes earlier, depending on season and location.
High latitudes: when twilight never ends
The further you are from the equator, the shallower the sun’s path. In summer at high latitudes the sun may not get deep enough below the horizon for Fajr or Isha to occur at all.
Example: London (51.5° N). At the June solstice, the sun’s lowest point at midnight is about 90° − 51.5° − 23.44° ≈ 15° below the horizon. It never reaches 18°, so from roughly mid-May to late July there is no astronomical moment for 18° Fajr or 17° Isha. Further north (Scotland, Scandinavia, northern Russia) the period is longer, and above the Arctic Circle the sun may not set at all.
Common solutions:
- Middle of the night: Isha no later than, and Fajr no earlier than, the midpoint between sunset and sunrise.
- One-seventh of the night: night is divided into seven parts; Isha begins after the first seventh, Fajr at the start of the last seventh.
- Angle-based: the night portion is proportional to the angle (e.g. 18/60 of the night for an 18° Fajr).
- Nearest latitude or nearest day: use times from a latitude (often around 45°–48.5°) or a date where the signs still occur.
Different communities adopt different rules, which is a major reason timetables in northern Europe disagree in summer.
Why your sources differ
- Different methods or angles for Fajr and Isha.
- Asr convention: standard vs Hanafi.
- Safety margins (ihtiyat or temkin): some authorities add a few minutes to certain times.
- High-latitude rule in summer.
- Location precision: using a city centre vs your exact position can shift times by a minute or two across a large city.
- Elevation and rounding of times to the minute.
- Daylight saving time settings on the device.
None of these differences is an astronomical “error”: each timetable is internally consistent with its chosen definitions.
The Islamic calendar and Ramadan times
Prayer times follow the solar day, but Islamic months follow the moon. Some authorities start months from calculated calendars (such as Umm al-Qura in Saudi Arabia), others from local moon sighting, so the start of Ramadan or Eid can differ by a day between countries. Our Hijri date converter converts between Gregorian and Hijri dates using a calculated calendar.
Checklist
- Set your exact location and correct time zone.
- Choose the calculation method used by your local mosque or national authority.
- Select the Asr convention (standard or Hanafi) that you follow.
- At high latitudes, check which twilight rule your timetable uses in summer.
- Compare with your local mosque’s printed timetable if two sources disagree.