Patents contribute to economic development; therefore, estimations of patent value are significant in measuring their impact on the economy. With this in mind, this article discusses estimations of patent value with the renewal model developed by several economists. Targeted patents are those issued in the United States and Japan from 1990 to 2010. In addition, the study examines patent values for several technology fields and considers which technology field should be the focus for the United States and Japan. Moreover, this article compares estimations based on the renewal model versus those based on other data such as sales, trade prices, or trials and analyzes how close this model's estimations are to the real values. This article's results demonstrate that the renewal model is useful for evaluating patents overall and analyzing technological trends from a patent perspective.