Appendix A:
Conductivity to TDS Conversion Factors
Conductivity
at 25 °C
23μS
84μS
447μS
1413μS
1500μS
2070μS
2764μS
8974μS
12,880μS
15,000μS
80mS
442: 40% sodium sulfate, 40% sodium bicarbonate and
20% sodium chloride
Appendix B: Calculating TDS Conversion Factors
The meter can be calibrated using TDS calibration
standard solutions. The calibration standard only needs
to give the TDS value at a standard temperature such as
25°C. To determine the Conductivity-to-TDS conversion
factor use the following formula:
Factor = Actual TDS ÷ Actual Conductivity @ 25°C
Definitions
Actual TDS: Value from the solution bottle label or as a
standard you make using high purity water and precisely
weighed salts.
TDS KCL
ppm
Factor
11.6
0.5043
40.38
0.4807
225.6
0.5047
744.7
0.527
757.1
0.5047
1045
0.5048
1382
0.5
5101
0.5685
7447
0.5782
8759
0.5839
52,168 0.6521 48,384 0.6048 79,688 0.9961
15
TDS (NaCL)
ppm
Factor
10.7
0.4652
38.04
0.4529
215.5
0.4822
702.1
0.4969
737.1
0.4914
1041
0.5029
1414.8 0.5119 2062.7 0.7463
4487
0.5
7230
0.5613 11,367 0.8825
8532
0.5688 13,455
TDS (442)
ppm
Factor
14.74
0.6409
50.5
0.6012
300
0.6712
1000
0.7078
1050
0.7
1500
0.7246
7608
0.8478
0.897