What is the volume of a drop of water?

The mass of a drop of water, m, hanging from a capiliary tube of radius a may be estimated by:

m = (2π a γ cosθ) / g

where:

γ is the surface tension of water = 72 x 10^-3 N m-¹ (at 25 ˚C in air)

θ is the water-glass contact angle ~ 14˚

g is the acceleration due to gravity 9.81 kg m s-²

the volume of the water droplet, V = m / ρ where ρ is density of water = 997 kg m-³ (at 25 ˚C).

Therefore V = (2π a γ cosθ) / ρg.

For a dropper of radius a = 2 mm, subsituting gives V ~ 1 x 10^-7 m³ or 0.1 cm³.

The volume of water drops does vary widely. You can easily verify this by dropping several drops from different sources and comparing the volumes or weighing them on an accurate Laboratory grade scale.

not all drops are the same size.

I couldn't hear it. So, its 0