Go to the app store and search chromatic tuner. This is the list it pulled up for me. I have found Cleartune to be the best. However there are a lot of options out there. Install app.
Here are the ratings for the app I use.
Grab your instrument! Below is a great resource to find the tuning of almost any instrument. tunings.pbworks.com
Start Tuning. Standard guitar tuning isbottom (fat string closer to your head also #6) to top (the thinnest string closest to the ground also #1). E A D G B E Have fun