Previous research into the teaching and learning of surface area emphasises the use of nets and formulae to calculate the total surface area of three-dimensional objects despite enduring student difficulties. This study investigated an instructional intervention for Year 8 mathematics students (n = 47; 13-14 years old) designed to elicit multiple strategies for calculating the surface area of simple prisms and justifications for choosing those strategies. I used the theory of strategy choice to analyse the collective strategy repertoire, flexibility, and adaptivity that students developed and used to calculate the total surface area of cubes and prisms. The results revealed that students developed a range of strategies and used them in varied combinations to calculate surface area. Students also developed a range of justifications for their strategy choices, which suggested that a focus on nets and formulae might not be appropriate when students are first learning to calculate surface area.