Tolerance of a ceramic capacitor
There really is no "generally speaking" for capacitor tolerance. Tolerances will vary greatly depending on manufacturer and intended usage. There are many tolerances for variety of purposes. Some are symmetrical (+/-20%) others are not (+80%/-20%). Some have very tight tolerances (for example for filtering) whereas others can be quite loose (bypass capacitors). 

Oleg's suggestion to measure the capacitor is a good one. Keep in mind that what you measure will also have a tolerance associated with it. Any measurement tool will have some amount of error. In addition, temperatures, humidity, and other environmental and electrical stresses can affect the value over time. a 100pf cap today at room temp and 40% humidity could be 60pf at 0°C and 10% humidity. Without knowing the specifics/manufacturer of the capacitor, the effects of these variations can only be known by testing them yourself.