An initial approach for scaling up geometrically dissimilar orbitally shaken bioreactors is presented. A novel ShakerBag Option for Multitron Cell shaking incubators allows a rapid increase in working volume from small TubeSpin bioreactors or shake flasks up to 10L, thus offering a simple and cost-efficient alternative to present systems for scale-up. The engineering parameters for scale-up of the orbitally shaken single-use bags were determined using traditional methods. Modern computational fluid dynamics based methods were used to gain a deeper insight into the fluid flow behavior. Furthermore, mass propagation of plant cell suspensions (Nicotiana tabacum and Vitis vinifera), as well as cell expansion and production of protein complexes using insect cells (Sf-9), show the potential of orbitally shaken single-use bags.