This textbook focuses on differential calculus, integral calculus and vector calculus for both undergraduate and postgraduate studies. It has well explained concepts and examples; including exercises at the end of every section. It contains four chapters: calculus I, calculus II, calculus III, and calculus IV. In the first chapter (Calculus I), the focus is on limits, continuity and derivatives of functions of a single variable; including their applications. In the second chapter (Calculus II), the focus is on curve sketching, hyperbolic functions and integration of functions of a single variable; including their applications. In the third chapter (Calculus III), the focus is on the precise definition of limits, L'Hopital's rule, Rolle's and mean value theorems, sequences and series, power series, partial differentiation, improper integrals, reduction formulae, double integrals, and matrix algebra; including their applications. In the fourth chapter (Calculus IV), the focus is on multivariable calculus - limits, continuity, Taylor's theorem, optimization, Fourier series, triple integrals, and vector calculus; including their applications.