When is a drop really a drop?

[Vapro]

I ml. equals 20 drops, right?

None of my dropper-tip bottles seem to know this. I measured them and always get less than a ml. Often quite a bit less. These must be "droplets"

Are they using a specific type of dropper when they measure or am I just so stupid I can't work an eye-dropper?!

 

[Spazmelda]

A 'drop' is not a standardized unit of measure. The volume of a drop depends on a few variables. Viscosity of the liquid matters (so composition and probably temperature would make a difference). The dropping container also matters (diameter of hole, etc...)

To know for sure you'd have to calibrate each dropper with each particular liquid by dropping into a graduated cylinder (or similar measuring device) and record the drops/ml for each liquid and each dropping device you plan on using.

This is why I dislike 'drops' as a unit of measure for DIY. It's just not as accurate as using a syringe or a pipette. For some applications drops are fine though; when you don't need to accurately know how much you are using.

 

[Eddie.Willers]

+1 what Spazmelda said.
'Drops' is possibly the least accurate way of measuring any liquid.