Particle Size Chart

Understanding Particle Sizes   (See Chart Below)

A water molecule is not a perfect sphere. The oxygen atom is flanked on either side by two hydrogen atoms at an angle of about 104.45 degrees. The distance from the center of the oxygen atom to the center of one of the hydrogen atoms is about 95.84 pm (picometers - trillionths of a meter), which equals 0.0000958 µm (micrometers, or microns).

A perfect sphere that would tightly encompass a water molecule is closely calculated to be about 0.000282 µm (micrometers - millionths of a meter) in diameter. You can say this number as "Two-Hundred Eighty-Two picometers" or (282 trillionths of a meter). Now that's small!

Note: See chart below where the water molecule (H2O) is located. The molecules CL2 is chlorine, and C6H6 is benzene. As you can see, these molecules are only slightly larger than a water molecule, and only very slightly larger than the largest pores in the RO membrane, 0.0005 µm ("half a nanometer", or "500 picometers").

These impurities will not fit through the pores of a Reverse Osmosis filter, and will be excluded from your drinking water.

    0.000282 ┬Ám (micrometers - millionths of a meter) equals,
    0.282 nm       (nanometers - billionths of a meter) equals,
282.0 pm           (picometers  - trillionths of a meter).

Basic geometric structure of a water molecule

Basic geometric structure of a water molecule.

Space filling model of a water molecule

Space filling model of a water molecule.


Particle Size Chart



The human eye is capable of seeing particles down to about 40 microns without the use of a microscope. Use this micron particle size chart to give you perspective on particle sizes.


Click to visit the top-rated Under Counter Water Filters page or the best Countertop Water Purifiers.