How Prayer Times Are Calculated: Methods, Fajr Angles, and Why Apps Differ

If you have ever opened two prayer apps side by side and seen a different Fajr time on each, you are not alone. It is one of the most common questions people ask, and the answer is not that one app is broken. Prayer times depend on the sun, and on a few choices about how to measure it. This guide explains those choices in plain language, so you know why the times differ and how to pick the one that suits you.

This is an explanation of how the calculations work, not a ruling. If your local mosque or religious authority publishes a timetable, following it is usually the safest and simplest option.

The basis: times come from the sun

The Quran and the Sunnah link the prayers to the position of the sun. Sahih Muslim records hadith that describe when each prayer begins and ends, for example the hadith narrated by Abdullah ibn Amr. Scholars and astronomers turned these descriptions into mathematical rules, so that the times can be worked out for any place on earth, on any day of the year.

To do this, a calculator needs three things: your latitude and longitude, the date, and the method (the set of rules for the twilight angles and the Asr shadow). The first two are facts. The third is where the differences come from.

How each prayer is defined

• Fajr begins at true dawn, when a thin line of light spreads across the horizon before sunrise. Astronomers measure this as the sun being a certain number of degrees below the horizon.
• Sunrise is when the top edge of the sun appears. It is the end of the time of Fajr, not a prayer time in itself.
• Dhuhr begins just after the sun passes its highest point (solar noon) and starts to decline.
• Asr begins when the shadow of an object reaches a set length. The length depends on the school of thought, as explained below.
• Maghrib begins at sunset, when the sun has fully set below the horizon.
• Isha begins when the red or white twilight has gone and the sky is dark. Like Fajr, it is measured by an angle below the horizon, or in some methods as a fixed time after Maghrib.

Why Fajr and Isha differ the most

Dhuhr, Maghrib and sunrise are easy to measure because they are tied to a clear event. Fajr and Isha are different. They depend on how many degrees below the horizon the sun is, and different organisations have chosen different angles, based on observation and scholarly opinion.

Some of the commonly used methods, with the angles they are usually described as using, are:

• Muslim World League: 18° for Fajr and 17° for Isha.
• ISNA (North America): 15° for both Fajr and Isha.
• Egyptian General Authority of Survey: about 19.5° for Fajr and 17.5° for Isha.
• University of Islamic Sciences, Karachi: 18° for both.
• Umm al-Qura (Makkah): about 18.5° for Fajr, and Isha set at a fixed interval after Maghrib (usually 90 minutes, longer in Ramadan).

These figures are the ones commonly published, and an authority can update its own method over time. The lesson is the same either way: a bigger angle means an earlier Fajr and a later Isha. Moving from 15° to 18° can shift Fajr by 20 minutes or more, depending on the season and the city. That is why two apps can disagree by that much without either being a mistake.

The Asr difference

There are two common ways to set Asr. In the first, Asr begins when the shadow of an object equals its own length (plus the shadow it had at noon). This is the usual view of the Shafi’i, Maliki and Hanbali schools. In the second, Asr begins when the shadow is twice the object’s length (plus the noon shadow), which is the view followed by the Hanafi school. The second gives a later Asr, usually by about an hour in summer. If your app has an Asr setting, set it to the school you follow.

Small adjustments: elevation, refraction and safety minutes

Some apps add a few minutes to account for the way the atmosphere bends light near the horizon, and for the height of the place above sea level. Others add a few minutes as a precaution, for example to make sure that Dhuhr has certainly begun. These adjustments are small, but they can explain a one or two minute gap between two apps that use the same method.

High latitudes: when the sky never gets fully dark

In places far from the equator, such as northern Europe, the sun may not go far enough below the horizon in summer for the usual angles to be reached. This means that the usual Fajr or Isha time cannot be calculated. Scholars and councils have given several solutions, such as dividing the night into parts, using the times of the nearest city where the signs are clear, or using a fixed interval. These methods give different results, so if you live in such a place, it is best to follow the timetable of your local mosque or council.

How to choose the right method for you

1. Follow your local authority or mosque. If there is an official timetable, use the same method in your app so the times match the community.
2. If there isn’t one, choose the method used in your country or region. For example, many people in South Asia use the Karachi method, and many in North America use ISNA.
3. Set Asr according to your school of thought.
4. Be careful with Fajr. If you are unsure, some people prefer to wait a few minutes after the listed Fajr time before praying. Ask a scholar if you want guidance for your situation.
5. Check the location. A wrong city or time zone is a more common cause of errors than the method.

You can use our prayer time tools page to see the prayer time tools on this site, and if you want to understand a method, compare the times for your city with your local mosque’s timetable for a few days.

Frequently asked questions

Why is my Fajr time different from my mosque’s?

The most likely reason is that the mosque uses a different angle. Ask the mosque which method it uses and set your app to match.

Which Fajr angle is correct?

Scholars and astronomers have differed on this, and the differences come from different observations and interpretations. There is no single answer that everyone agrees on, so follow the practice of your local scholars.

Do prayer times change every day?

Yes. As the length of the day changes through the year, the times shift by a minute or so each day, and more quickly in spring and autumn.

Is it a problem if my app is a few minutes off?

Small differences are normal. The main point is to pray within the correct time and not to start before it. If you are unsure, wait a little.

Sources and further reading: Sahih Muslim (the chapter on the times of prayer); the published calculation methods of the Muslim World League, ISNA, the Egyptian General Authority of Survey, the University of Islamic Sciences (Karachi) and Umm al-Qura. Method details are updated by their authorities from time to time, so please check the current published method if you need exact figures.