DTA measurements were performed to obtain the crystallization peak temperature, T C , for Li 2 O.2SiO 2 glass heat-treated for nucleation. The relationship between T C and the number density of nuclei was obtained. Calculation of T C was performed by simulating the crystallization process, and the effects of the size and the number density of nuclei formed during DTA measurement on T C was evaluated. The calculated relationship between the number density of nuclei and T C agreed with the experimental one, and it was shown that the effects of the size and the number density of nuclei formed during DTA measurements is negligible in the evaluation of the number density of nuclei by T C . The steady state nucleation rate for the Li 2 O.2SiO 2 glass evaluated by DTA agreed well with the literature.