Turbidity Tube Conversion Chart

The Turbidity Conversion Chart converts the measured value in cm to Nephelometric Turbidity Units (NTUs).  This is the official unit of measurement to quantify how much light is scattered due to the suspended sediments.  You can convert your turbidity tube reading from a height to NTUs using the chart below.

Distance from Bottom of Tube (cm)

NTUs
<6.25 >240
6.27 to 7 240
7 to 8 185
8 to 9.5 150
9.5 to 10.5 120
10.5 to 12 100
12 to 13.75 90
13.75 to 16.25 65
16.25 to 18.75 50
18.75 to 21.25 40
21.25 to 23.75 35
23.75 to 26.25 30
26.25 to 28.75 27
28.75 to 31.25 24
31.25 to 33.75 21
33.75 to 36.25 19
36.25 to 38.75 17
38.75 to 41.25 15
41.25 to 43.75 14
43.75 to 46.25 13
46.25 to 48.75 12
48.75 to 51.25 11
51.25 to 53.75 10
53.75 to 57.5 9
57.5 to 60 8
Over the top 6