This study focuses on landslide volume evaluation methods and their applicability to large-scale landslides. Historical data from six large-scale landslides were used to estimate landslide volumes by power-law formulas (area versus depth or area versus volume). The results show the estimated volumes are undervalued. A new landslide volume evaluation method was carried out to improve the precision of the landslide volume evaluation. This method was created by landslide area and volume from the historical records and is shown in terms of a polynomial regression equation with an R-squared value of 0.97. The landslide areas among 30 ha and 400 ha were verified to properly fit this equation and will be utilized as the simple estimation method.