The capacitors in parallel combination is shown in Figure 1 where all the left plates are connected to one terminal (in this case positive terminal) of a battery and right plates are connected to another terminal (in this case negative) form a parallel combination of the capacitors.
The potential differences across all capacitors in parallel are the same as that of the battery as all the left plates are connected to one terminal and right plates to another.
All the capacitors in parallel have the same potential difference but the charges on the capacitors are not the same unless the individual capacitances are the same.
In the Figure 1shown one capacitor has capacitance \(C_1\) and the other has capacitance \(C_2\). Then, the charges on the capacitors \(Q_1\) and \(Q_2\) due to the same potential difference \(V\) are \(Q_1 = C_1V\) and \(Q_2 = C_2V\) respectively.
The total charge of the combination \(Q\) is
\[Q = Q_1 + Q_2 = V(C_1+C_2)\]
The equivalent capacitance of the combination is \(C_\text{eq} = Q/V\) is
\[C_{\text{eq}} = C_1+C_2\]
In the similar way for any number of capacitors in parallel combination the equivalent capacitance is
\[C_{\text{eq}} = C_1 + C_2 + C_3 + ...\]
As you can see the equivalent capacitance in parallel combination is always greater than any of the individual capacitances and equal to the algebraic sum of all capacitances.
