You can also just input the tank size and approximate the WC, but dimension work best OFC.
I did take a while but it was like a maths puzzle which I like, so enjoyed the challenge. Plus if folk use it it checks the maths so checks my ferts at the same time. Plus always good to help others at the same time. I am very pleased with the 'Headshot Wizard' and the 'Clone Wizard' is a delight. Any errors please give feedback or additions also. I do have PO4 to add to the water report as the OP was the first water report I've seen with PO4 in the tap water.