Factors for calculated carbon dioxide concentrations in water with known
pH, temperature and alkalinity measurements.

For example, if the water measurements are as follows:

Temperature = 25° C
pH = 6.8
KH = 50 mg/L

The multiplicative value to use for a pH of 6.8 and Temperature of 25°C = 0.313
(see chart below)

KH x Chart Value = mg/L CO2
example: 50 x 0.313 = 15.65 mg/L CO2

Temperatures ( ° Centigrade)
pH	5	10	15	20	25	30	35
6.0	2.915	2.539	2.315	2.112	1.970	1.882	1.839
6.2	1.839	1.602	1.460	1.333	1.244	1.187	1.160
6.4	1.160	1.010	0.921	0.841	0.784	0.749	0.732
6.6	0.732	0.637	0.582	0.531	0.495	0.473	0.462
6.8	0.462	0.402	0.367	0.335	0.313	0.298	0.291
7.0	0.291	0.254	0.232	0.211	0.197	0.188	0.184
7.2	0.184	0.160	0.146	0.133	0.124	0.119	0.116
7.4	0.116	0.101	0.092	0.084	0.078	0.075	0.073
7.6	0.073	0.64	0.058	0.053	0.050	0.047	0.046
7.8	1.046	0.040	0.037	0.034	0.031	0.030	0.030
8.0	0.029	0.025	0.023	0.021	0.020	0.019	0.018
8.2	0.018	0.016	0.015	0.013	0.012	0.012	0.011
8.2	0.012	0.010	0.009	0.008	0.008	0.008	0.007
Factors should be multiplied by total alkalinity (mg/L) to get carbon dioxide (mg/L). For practical purposes, CO2 concentrations are negligible above pH = 8.4 Tucker (1984)

Temperatures ( ° Centigrade)