It tells me that my BMI is 24.2, which is within the normal range, and says I don't need to loose weight. Yet I am clearly carrying too much weight for my frame, confirmed by the 30% fat it's calculated against my neck measurements!
I think there is a huge element of knowing what's right for you in all this. I've been 36lb lighter than I am right now and I was the fittest, healthiest and most energetic I've ever been in my life. It really doesn't suit me being the weight I am now.
Two people the same height can be so different too. My MIL is the same height as me, yet my hands are smaller, my feet are two complete shoe sizes smaller, my rib cage/hips/shoulders are all substantially smaller/narrower than hers. So it's not surprising that if she drops below the weight I am now she feels unwell, yet me at this weight is horribly uncomfortable.
I do like to track my body fat though, and the amount of weight sustaining protein/calories I need which is why I like the measurement calculator. I find the scales aren't that good for accurate body fat.