Numerical simulations are prepared to investigate the influence of small casting speed variations between 715 and 735 mm min−1 on the metallurgical length in continuous casting of 285 mm thick steel slabs. The effect of considering/ignoring the melt flow in the numerical continuous casting model for predicting the metallurgical length is also investigated. The simulations are based on an Eulerian two-phase solidification model including melt (liquid phase) and columnar dendrites (solid phase). Solidification of a binary Fe–C-alloy is calculated. Two 25 m long straight strand geometries of industrial scale are modeled. Both of these geometries have waved surfaces to consider periodical strand surface bulging. In order to consider a defined mechanical softreduction (MSR) configuration as well, the cross-section of one of these geometries decreases at a rate of 1 mm m−1 within a defined length. For a given casting configuration and for defined cooling conditions, the influence of small casting speed variations on the metallurgical length, on the average solid fraction and on the enthalpy flux are determined. The simulation results can be used to optimize the settings for operating continuous casting plants, e.g., to adapt the MSR position.