To check for sperm using a home microscope you should first be sure to set the microscope to 400x magnification or higher.
Next, place a small drop of semen on a clean slide and cover with a square coverslip (22mm x 22mm). To judge the correct size of the drop, the semen should just fill in under the cover slip. If any flows out, the drop is too big. If it does not fill in under the entire cover slip, the drop is too small. Try to examine several 400X fields and pick one that seems to best represent the sample in number of sperm seen.
Next, count the number of sperm observed, both motile (swimming) and non-motile (not swimming). Divide this number by half and you will get an approximate sperm density. This density (or count) is in the units of millions of sperm per milliliter, or M/ml.
You can also calculate the percent motility (percentage of sperm swimming) using this same slide and arrive at a fairly accurate result.
Count 100 sperm (or as close to this number as you can observe) and make a note of which ones are motile (swimming) and which are not. Divide the number of sperm that were motile by the total number of all sperm seen, multipy this fraction by 100, and you have the percent motility.
For example, if you observed 35 sperm motile out of 100 sperm observed,
35 / 100 = 0.35 x 100 = 35% motility. The reference interval (normal range) for sperm motility is 50% or greater.
Please in mind this is a rough estimate only, and is not the method used by laboratories to caculate an accurate sperm density. The reference interval (normal range) for sperm density is 20 to 120 M/ml.