I use Strelok ballsitic calcualor (4.5 / 5 stars) and just came across the Sierra loading manual for Android (3.5 / 5 stars) Trying to figger out the Hornady e-manual.
I would say applied ballistics except i'm almost 1/2 years in to having it and still cannot get all three devices to work together . but the program seems to be nice on others phones .
The Hornady 4DOF works well especially if you are shooting their bullets and has data entry points for your load data. Most other apps will allow you to put info in the notes section. Stelok has a good reputation and there are many others: Trasol, GeoBallistics, Applied Ballistics, etc. I would give the free ones a go as you have nothing to lose.
Shooter runs well on an iPhone. Not the newest, and needs some updates but you can add bullets manually. It does allow banded BCs. Its been accurate for me.
I have both AB Mobile (Applied Ballistics) and Ballistic AE on my iPhone. I like both but prefer AB Mobile. It’s seems less user friendly, but has more features and seems to give more accurate results. Your mileage may vary.
Trasol for iphone is my go to outside of my Kestrel AB. I use both, and compare to make sure they’re both on the same page and then just stick to my Kestrel for field work.
The Trasol HUD is pretty cool though and I use it to determine mover speed and angles