This tool will check all meridians and find the max power at any meridian. Ametropia could easily be calculated by adding sphere to cyl since you get total power at 90 degrees. Anisometropia is the difference between the eyes in any meridian so it's much more complex.
You could enter the Rx into Eyefinity for your VSP claim and they will calculate it for you, but you have to enter an entire claim just to check an Rx. We decided to make our calculator publicly available, since nobody else on the internet has one.
If you aren't aware of what insurance covers this condition, this article is a short writeup that is mostly correct. He mentions High Ametropia exceeding –10D or +10D is based on spherical equivalent, but it's based on the meridian as well. See page 46 of the 2024 EyeMed manual.
This article has more detail and is much more accurate.
If you aren't sure how to calculate the power for one eye, this article provides a detailed explanation on that calculation.
Minus Cyl only folks. For now.