Any Speed Tested Calculator Building apps?

[LSAccounting]

I am using the Spark Theme. 

Currently on Calconic Calculator builder which is free and worked very well however, unfortunately it is one of the main things causing issues with speed score.

Does anyone know of alternatives? I use it for things like calculating mortgage repay rates, savings etc. 

Unless there is a way of importing Excel Data into a page which will be able to be adjusted by viewers? 

TIA