Variable units of measurement

Hi

I am trying to create a calculator that works out the volume of water based on shape/size of container.

I have a dropdown that allows the user to select the shape of the container and then some fields for them to input length, width, height etc.

Certain containers require additional measurement fields, such as radius or diameter, but I only want those fields to show when necessary based on the type of container, which doesn’t seem to be working.

In addition I would like the user to be able to select the unit of measurement, such as cm, mm, in. Again I have created a dropdown for this, however I’m unable to only show the required measurement fields based on the container selected.

Is there a better way to allow users to select variable units of measurement?