If you have a goal set to acheive a certain level use the Goal Calculator. If you want to know how many more points you need to reach the next level then use the Level Calculator. When no points are entered or 0 is entered it sometimes causes a misfire in the calculations. If the goal level chosen is lower than the points entered you will see the error message.
This will now calculate up to the current top level 70. They are using the same level titles for levels 9 and 44, 16 and 42, the name changed slightly for level 29.