How Prayer Times Are Calculated
The Quran states that "prayer has been decreed upon the believers at specified times" (An-Nisa 4:103) and references the sun's movement as a marker: "Establish prayer at the decline of the sun until the darkness of the night, and the recitation of dawn" (Al-Isra 17:78). Islamic prayer times are therefore determined by the position of the sun relative to the observer. Unlike fixed clock times, they shift throughout the year as the sun's path across the sky changes with the seasons. This guide explains the astronomical principles behind each prayer time.
The Sun's Position
The Earth rotates on a tilted axis as it orbits the sun, causing the sun's apparent path across the sky to change daily. Two key measurements matter for prayer times: the sun's altitude above the horizon and its hour angle relative to the local meridian. At solar noon, the sun crosses the meridian at its highest point of the day. In summer, the sun reaches higher altitudes and the day is longer; in winter, the opposite. These seasonal shifts cause prayer times to change throughout the year.
Fajr — The Dawn Prayer
Fajr begins at astronomical dawn, when the first light appears on the eastern horizon. This occurs when the sun is a specific angle below the horizon — typically between 15° and 19.5°, depending on the convention used. The Muslim World League uses 18°, while ISNA uses 15°. A smaller angle means a later Fajr time. At high latitudes during summer, the sun may not dip far enough below the horizon for true astronomical dawn, requiring special calculation methods.
Sunrise
Sunrise marks the end of the Fajr prayer window. It is calculated as the moment the sun's upper limb appears on the horizon, accounting for atmospheric refraction — the bending of light through the atmosphere that makes the sun visible slightly before it geometrically clears the horizon. A standard refraction correction of about 0.833° is applied to all sunrise and sunset calculations.
Dhuhr — The Noon Prayer
Dhuhr begins shortly after solar noon — the moment when the sun crosses the local meridian and shadows are at their shortest. A small safety margin of 1-2 minutes is added after solar noon to ensure the sun has definitively passed its zenith. Solar noon itself shifts throughout the year due to the equation of time, which accounts for Earth's elliptical orbit and axial tilt. This is why clock noon and solar noon rarely coincide.
Asr — The Afternoon Prayer
Asr is determined by shadow length. The Shafi'i method (standard in most conventions) begins Asr when an object's shadow exceeds its noon shadow by the object's own height (shadow factor 1). The Hanafi method uses twice the object's height (shadow factor 2), resulting in a later Asr time. This shadow-based definition ties Asr directly to the sun's altitude — as the sun descends, shadows lengthen, eventually reaching the threshold.
Maghrib — The Sunset Prayer
Maghrib begins immediately after sunset, defined as the moment the sun's upper limb disappears below the western horizon. Like sunrise, this includes atmospheric refraction corrections. Maghrib generally has a relatively short prayer window, lasting until Isha begins. In most conventions there is no calculation parameter for Maghrib — it is simply the moment of sunset.
Isha — The Night Prayer
Isha begins when twilight on the western horizon disappears. The Shafi'i and majority position uses the disappearance of red twilight (shafaq al-ahmar), while the Hanafi position uses the later white twilight (shafaq al-abyad). Conventions typically use sun depression angles between 14° and 18°. The Umm al-Qura method uses a fixed 90-minute interval after Maghrib instead of an angle. At high latitudes in summer, twilight may persist all night, requiring special adjustment methods such as using the nearest day when Isha is calculable.
Calculation Conventions
Different Islamic authorities have established slightly different angle parameters based on their regional observations and scholarly traditions. The Muslim World League, ISNA, Egyptian General Authority, Umm al-Qura University, University of Karachi, Institute of Geophysics Tehran, and Jafari method each define their own Fajr and Isha angles. The differences typically result in variations of 10 to 30 minutes between methods for the same location.
This content is based on astronomical calculations and scholarly traditions. For religious rulings, please consult your local Islamic authority.
Prayer times by city