Short answer
In the Hanafi school a period (hayd) lasts at least 3 days (72 hours) and at most 10 days (240 hours). The clean gap between two periods is at least 15 days. Bleeding outside these limits is istihadah, not a period. The Shafi'i and Hanbali schools set the minimum at one day and the maximum at 15.
Minimum hayd 3 days and nights, maximum 10 days and nights, minimum purity between two periods 15 days, with no maximum. Hayd is possible from the age of 9 lunar years until menopause (about 55 on the relied-upon view).
Other madhhabs
- Shafi'i
- Minimum one day and night, maximum 15 days; minimum purity 15 days.
- Maliki
- No minimum for the purposes of prayer, so even a spurt counts; maximum 15 days, with extra days for some women.
- Hanbali
- Minimum one day and night, maximum 15 days; minimum purity 13 days.
Explanation
The Quran calls menstruation a harm and tells husbands to keep away from intercourse during it, but it does not give numbers. The schools took the limits from reports of the Companions and from what women around them actually experienced. The Hanafis rely on reports from Companions such as Anas that the period is 3 to 10 days, and they treat the several narrations together as strong enough to act on.
What the numbers mean:
- Under 3 days: the bleeding is istihadah (irregular bleeding). Wudu and prayer continue.
- 3 to 10 days: all of it, including brown or yellow at the start and end, is your period.
- Over 10 days: your usual number of days is the period and the rest is istihadah. See period lasting more than 10 days.
- Gaps: a clean day inside the 10 days, with bleeding on both sides, is counted as part of the period.
- 15-day gap: bleeding that starts less than 15 days after the last period ended is not a new period.
Your habit (adah) is the number of days your period normally lasts and where it falls. The Prophet ﷺ told women with ongoing bleeding to leave prayer for the number of days they used to menstruate. So keep a simple record of the day and time each period starts and ends.
A period ends when the bleeding stops and you see pure white or nothing at all. Then you make ghusl: see how to do ghusl.
The evidence
Quran, Surah Al-Baqara 2:222
وَيَسْـَٔلُونَكَ عَنِ ٱلْمَحِيضِ ۖ قُلْ هُوَ أَذًۭى فَٱعْتَزِلُوا۟ ٱلنِّسَآءَ فِى ٱلْمَحِيضِ ۖ وَلَا تَقْرَبُوهُنَّ حَتَّىٰ يَطْهُرْنَ ۖ فَإِذَا تَطَهَّرْنَ فَأْتُوهُنَّ مِنْ حَيْثُ أَمَرَكُمُ ٱللَّهُ ۚ إِنَّ ٱللَّهَ يُحِبُّ ٱلتَّوَّٰبِينَ وَيُحِبُّ ٱلْمُتَطَهِّرِينَ ﴿٢٢٢﴾
And they ask you about menstruation. Say, "It is harm, so keep away from wives during menstruation. And do not approach them until they are pure. And when they have purified themselves, then come to them from where Allah has ordained for you. Indeed, Allah loves those who are constantly repentant and loves those who purify themselves."
Establishes menstruation as a state with its own rulings.
Sahih al-Bukhari 325
Sahih... دعي الصلاة قدر الأيام التي كنت تحيضين فيها ...
"Leave the prayer for the number of days you used to menstruate, then bathe and pray."
Shows that a woman's habit decides her period days when bleeding continues.
Where the ruling is recorded
- al-Hidaya, Kitab al-Taharah, chapter on menstruation and istihadah. Minimum three days, maximum ten, minimum purity fifteen.
- Nur al-Idah with Maraqi al-Falah, Chapter on menstruation, postnatal bleeding and istihadah. A clear summary of the limits.
- al-Mughni (Ibn Qudama), Kitab al-Hayd. Hanbali limits of one day and fifteen days.
This answer is pending review by the scholars on our team. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.