Answered by: Alimah Sabrina al-Faarsiyyah
1. Few people say that if the length of hair is more than (1/3) of the finger then only trimming is allowed and valid. A few say the length is irrelevant and it should be removed from all overhead. Which is correct?
2. Is the trimmer setting at Zero considered a razor?
3. I did Umrah and removed all my hairs with a zero trimmer and did again a second Umrah after 2-3 days and used zero trimmer to remove all hairs (whichever the trimmer could do). The length of hairs will not be (1/3) of the finger as it is difficult to grow in just 2-3 days. Is it valid?
4. In the future, can I use zero trimmer even if I have little hair or should I use a blade?
After 2 umrahs, I used a blade (to be safe) for the next umrahs and Hajj.
Is there any dam on me? I was just checking as a few people say that the length should be (1/3) to cut but I also heard that zero trimmer is equivalent to the razor as it removes all hairs.
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
Both shaving and trimming are permissible for people whose hair length is more than a third of a finger, although shaving is more virtuous. For people whose hair length is less than a third of their finger, then they must shave at least a fourth of their head as the minimum of hair that they must remove is a third of a finger on a fourth of their entire head.
Only Allah knows best
Written by Alimah Sabrina al-Faarsiyyah
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Tahtawi, Hashiyah, DKI 1/736 + Ascent to Felicity pg.157
ثم يحلق أو يقصر والحلق أفضل ويكفي فيه ربع الرأس والتقصير أن يأخذ من رؤوس شعره مقدار الأنملة