Calculation method
Institute of Geophysics, University of Tehran
The Institute of Geophysics, University of Tehran method places Fajr when the sun is 17.7° below the horizon and Isha 14° below the horizon. Maghrib is at sunset. It is conventionally used in Iran.
| Fajr angle | 17.7° |
|---|---|
| Maghrib | at sunset |
| Isha | 14° below the horizon |
| Used in | Iran |
What does the Fajr angle mean?
Fajr begins at true dawn, when the first light appears along the horizon. Astronomically that is expressed as the sun being a set number of degrees below the horizon — here 17.7°. A larger angle means an earlier Fajr.
How this method differs from the others
All nineteen methods agree on Dhuhr, Asr and Maghrib, because those are fixed by the sun's position and by shadow length rather than by convention. They differ only on Fajr and Isha, which begin when the sun sits a set number of degrees below the horizon — and that number is a judgement about when dawn first appears and when the last light leaves. Tehran uses 17.7° for Fajr. A larger angle means an earlier Fajr and a later Isha; a smaller one, the reverse. Between the widest and narrowest methods the difference can reach half an hour at temperate latitudes, and more in summer further north.
Should you use it?
Use the method your local mosque or national authority uses. Praying in step with the congregation around you matters more than matching any particular calculation, and a method is a convention adopted by a body rather than a fact to be got right. Tehran is the convention in Iran. If you are elsewhere, your local authority's choice is the one to follow.
Common questions
What Fajr angle does Tehran use?
Tehran places Fajr when the sun is 17.7° below the horizon.
When does Isha begin under Tehran?
Isha is 14° below the horizon.
Where is Tehran used?
It is the conventional method in Iran.
See it applied
Calculate for your own location · How prayer times are calculated
The other calculation methods
Methods differ only in the Fajr and Isha angles; every other prayer follows from the sun directly. The angle each one uses is given below.
- Egyptian Fajr 19.5°
- Muslim World League Fajr 18°
- ISNA Fajr 15°
- Umm al-Qura Fajr 18.5°
- Karachi Fajr 18°
- Qum (Jafari) Fajr 16°
- Algeria Fajr 18°
- Diyanet Fajr 18°
- Egyptian (Bis) Fajr 20°
- Fixed Isha Fajr 19.5°
- France 12° Fajr 12°
- France 15° Fajr 15°
- France 18° Fajr 18°
- JAKIM Fajr 20°
- MUIS Fajr 20°
- KEMENAG Fajr 20°
- Tunisia Fajr 18°
- UAE Fajr 19.5°
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