This is a textbook for integral calculus with explanations, examples, worked solutions, problem sets and answers. It has been reviewed by calculus instructors and class-tested by them and the author. The definite integral is introduced by Riemann sums as a way to evaluate "signed" areas, and the text contains the usual theorems and techniques of a first course in calculus. Besides technique practice and applications of the techniques, the examples and problem sets are also designed to help students develop a visual and conceptual understanding of the main ideas of integral calculus. The exposition and problem sets have been highly rated by reviewers.