Background <p>T50 calciprotein crystallization test (serum calcification propensity, T50) is a blood test which assesses the resistance of the serum to calcification stress <i>in vitro</i>. Because of its limited availability in clinical practice of chronic kidney disease, we aimed to develop equations for estimated T50 (eT50).</p> Methods <p>This was an observational study in 1,651 hemodialysis patients whose T50 was measured by the method Pasch et al. The data sets were divided into two groups for the derivation (<i>N</i> = 1,003) and validation (<i>N</i> = 648) of the equations. Logarithmically transformed values of measured T50 were regressed by relevant variables selected from 36 candidates based on the Akaike’s Information Criteria.</p> Results <p>Because the initial model A included 19 variables, we developed simpler models B and C with 10 and 5 variables, respectively, for clinical use. All these models included serum phosphate, magnesium, sodium, chloride, and total ion binding capacity. When these equations were validated, the intercept, slope, and R² values were 1.130, 0.770, 0.596 for model A, 1.093, 0.782, and 0.597 for model B, and 0.979, 0.806, and 0.573 for model C, respectively. Multivariable-adjusted Fine-Gray analysis showed that a lower eT50 value by model A, B, or model C was an independent predictor of a higher risk of new cardiovascular events in the total cohort as the measured T50 was.</p> Conclusions <p>We developed three equations for eT50 from clinically available variables. These eT50 values may be useful if measured T50 is not available.</p>