I often have to travel out of my city for business trip, I usually go to trip ranging from 7 to 15 or more days, please clarify in details after how many days qasr namaz will have to offer?

Answered according to Hanafi Fiqh by Darulifta-Deoband.org

بسم الله الرحمن الرحيم

(Fatwa: 310/257/B=01/1435)

The ruling of journey shall be applicable on you when you leave your place or its surroundings on a journey of 77.25 kms or more than it and stay there less than fifteen days and it shall be wajib for you to offer salah with qasr. But if you intend to stay for fifteen days or more in the same place or the place is on a distance less than 77.25 kms then you will have to offer full salah.

Allah knows Best!

Darul Ifta,
Darul Uloom Deoband