==Evaluation==
[[File:CT measurement of kidney stone in soft tissue and bone window.jpg|thumb|Measurement of a 5.6 mm large kidney stone in soft tissue window (at left, with width of 400 HU, and center at 50 HU) versus skeletal window (right, W1800,C400). 145 HU is regarded as an appropriate cutoff to distinguish stone from surrounding tissue.<ref name="LidénThunberg2015">{{cite journal|last1=Lidén|first1=Mats|last2=Thunberg|first2=Per|last3=Broxvall|first3=Mathias|last4=Geijer|first4=Håkan|title=Two- and three-dimensional CT measurements of urinary calculi length and width: a comparative study|journal=Acta Radiologica|volume=56|issue=4|year=2015|pages=487–492|issn=0284-1851|doi=10.1177/0284185114528490}}</ref>]]
The proper sizing of a stone is most critical at around 5 mm.<ref name="Size" group="note"/>