Finite Element Analysis (FEA) is a powerful tool for calculating reinforced concrete structures. The ability to utilise the full nonlinear behaviour of concrete and reinforcement allows designing with the maximum capacity of a concrete structure, thus gaining more insight in the structural behaviour and increasing the structural reliability. The amount of reinforcement is often based on code rules (cross-sectional design) or simple linear-elastic calculations. The determined reinforcement is then used to perform a finite element calculation to check whether enough reinforcement is used. This procedure seems illogical, as the amount of reinforcement is still determined by simple rules. Especially for complex structures (e.g. complex loading or geometry), this could lead to conservative or even to inaccurate reinforcement designs. This paper presents a procedure to determine the amount of reinforcement for (complex) concrete structures using FEA. The finite element package DIANA is used for this procedure. The idea is to estimate the amount of reinforcement using stresses and/or forces in a 3D environment. From here the reinforcement can be optimized using nonlinear FEA. The procedure is applied on a membrane slab and a concrete pile cap foundation, but can be used for any geometric shape.