Unit of capacitance:

When the battery is connected between the plates of a capacitor, it takes some time before electric field reaches the full intensity of it. The voltage builds up at a rate which depends on the capacitance: greater the capacitance, slower will be the rate of change of voltage in plates.

The unit of capacitance is the expression of the ratio between amount of current flowing and rate of voltage change across the plates of a capacitor. A capacitance of one farad, represented as F, represents a current flow of one ampere while there is a potential-difference increase or decrease of 1 volt per second. A capacitance of 1 farad results in 1 volt of potential difference for an electric charge of 1 coulomb.

The farad is unit of capacitance. You will never see a capacitor with a value of 1 F. Commonly employed units of capacitance is microfarad (µF) and picofarad (pF). A capacitance of 1 µF represents the millionth (10^-6) of a farad, and 1 pF is the millionth of a microfarad, or the trillionth of a farad (10^-12 F).

Some large capacitances can be stuffed into physically smaller components. On the other hand, some capacitors with small values take up the large volumes. The bulkiness of the capacitor is proportional to voltage which it can handle, more than it is related to capacitance.