Calculations:
We can see from the balanced equation that the stoichiometric relationship between NaOH and KHP is 1:1. At the endpoint then:

   (eqn. 1)

Remember that:

   (eqn. 2)

and
   (eqn. 3)

Substituting eqn. 2 and eqn.3 into eqn. 1 gives eqn. 4:

   (eqn. 4)

Solving for Molarity NaOH, we obtain:

   (eqn. 5)

Since the definition of Molarity is moles of solute per liter solution, the volume of NaOH must be converted to liters.