Biopharmaceutical manufacturing capacity costs are around $3000 per liter of bioreactor ca-pacity. Moderate to large facilities can cost hundreds of millions, yet such investments are of-ten made with uncertain information about process performance, media and materials prices, and market conditions. This paper presents a systematic way to evaluate the critical costs and capacity issues in biotech plants. Examples will be presented on determining the target prod-uct titer, optimizing bioreactor batch size and choosing where or whether to use disposable equipment. Because many process decisions must be based on partial or uncertain information, this presentation will also describe how to evaluate the risk associated with process and eco-nomic assumptions.