The ongoing outbreak of the novel coronavirus (COVID-19) started from Wuhan, China, at the end of December 2019. It is one of the leading public health challenges in the world because of high transmissibility. The first patient of COVID-19 was officially reported on March 8, 2020, in Bangladesh. Using the epidemiological data up to October 17, 2020, we try to estimate the infectious size. In this paper, we used Classical SIR (Susceptible- Infected-Recovered), model. The epidemic has now spread to more than 216 countries around the world. The necessary reproduction number R_o of Bangladesh is 1.92. The primary data was collected from the Coronavirus (COVID-19) Dashboard (BANGLADESH: CASE TREND). In our analysis, the statistical parameters specify the best import to provide the predicted result. We projected that the epidemic curve pulling down in Bangladesh will start from the first week of November (November 4, 2020) and may end in the last week of July (July 24, 2021). It is also estimated that the start of acceleration on May 24, 2020, in 53 days, and the start of steady growth on September 10, 2020, in 109 days. The start of the ending phase of the epidemic may appear in the first week of November 2020, and the epidemic is expected to be finished by the last week of July 2021. However, these approximations may become invalid if a large variety of data occurs in upcoming days.