Nematode counts from soil may be expressed on a weight basis (#/g, #/100 g, #/250 g, etc.) or volume basis (#/250 cc, #/pint, #/quart, etc.). Counts may be expressed on the basis of wet soil or on the basis of dry soil, i.e. corrected for the amount of moisture in the soil. Generally, counts based on weight are more precise than those based on volume because it is easier to weigh out soil consistently than it is to measure the volume of soil consistently. However, if adjustment is not made for the amount of water in the soil, counts based on weight will be highly variable depending on the amount of moisture in the soil at time of processing.

Nematode counts from roots or other plant material are usually expressed as #/g tissue but this may be fresh weight or dry weight depending on the lab processing the samples.

If you work with only one laboratory, units of expression are less of a problem, as long as that laboratory is consistent, because once you learn how to interpret a particular laboratory's results, nematode counts on different reports are relative to each other. However, determining the meaning for your counts may still be awkward if you have to look into the literature and the research results are reported in different units than your lab results.