The Tubular PO4 Resorption (TRP) calculator would be enhanced tremendously by taking the arithmetic forward to the logical and clinically relevant conclusion: the tubular maximum resorption of phosphate, TmP/GFR. This would really benefit from an automatic calculation because TmP/GFR is calculated in two different ways depending on the TRP value.
1. When TRP is less than 0.86, TmP/GFR is simply TRP x serum phosphate.
2. When TRP is greater than 0.86, TmP/GFR is [serum phosphate][0.3TRP/(1-0.8TRP)

A web calculator is here:
http://baspath.co.uk/calculations/renal_tubular_reabsorption_of_ph.htm

A normal range is here:
http://www.mayomedicallaboratories.com/interpretive-guide/?alpha=T&unit_code=88546