The error analysis in the determination of interfacial tension and contact angle using sphere tensiometry was fulfilled using the total differential analysis. The average error in interfacial tension for all three methods (the maximum force point method, two points method (F0 and H0/R) and process curve method) is smaller than 0.05 mN/m and average error in contact angle is smaller than 0.9 degrees. Copyright 1999 Academic Press.