If you are using electrolytic capacitors, you should know that their error is in general quite large and can be up to +40% of the marked value.
Unless your capacitor is used as a component that determines a certain frequency, in applications like oscillator or filters, there is no added advantage of using two capacitors in series if the purpose of the capacitor is simply for bypassing. In fact a single capacitor is often better than two in series.
You would need to tell us how the capacitor is to be used in circuit or simply show us the circuit.