Calculate jitter of oscillator from PPM
The ppm spec on an oscillator is the accuracy and is (usually) specified over temperature and initial calibration. It says nothing about jitter. You will need to measure it or check the datasheet. 

Here's a jitter spec on a typical oscillator (10MHz CTS type)



So the peak-to-peak period jitter is less than 50 picoseconds for this part. JEDEC definition of peak-to-peak is +/-3\$\sigma\$. In theory the maximum jitter is unbounded (as Rimpelbekkie says) so you need to define an acceptable error rate or something of that ilk in order to talk about maximums.