Question: how to calculate hco3 from ph and pco2?
Answer: Normal values: HCO3: 22-26 meq/L. PCO2: 35 - 45 mmHg. pH: 7.35 - 7.45. ... 
Quick derivation: Carbonic acid (H2CO3) equilibrium: [H+] x [HCO3-] <---> [H2CO3] <---> [CO2] x [H2O] [H+] x [HCO3-] = K x [CO2] x [H2O] ... 
Final: pH = 6.1 +log (HCO3-/ (0.03 x PCO2))