You can calculate pH if you know the concentration of the NaOH.
You will need to know the molarity of the NaOH. Let's assume the solution is 0.1M. NaOH is a strong base, so this will produce 0.1mol/L of OH ions in solution. This will produce a pH of 13.
You will need to take the negative log of 0.1 to find the pOH. This will work out to be 1.
We can calculate the pH to be 13.
This assumption we made about the base can only be used for strong bases which dissociate completely in water.