I've not made my first batch of lotion for use yet but have done a bit of reading. So, I am no expert by any means but from what I've read the ph should be somewhere between 4 & 7 with 5.5 to 6.5 being the most common range that most shoot for. However if you have sensitive skin you may want to opt for the lower ph level. As for the best way to test I understand you can get ph strips.