可扩放性(Scalability)是指问题规模和处理器数目之间的函数关系。

可扩放性实际上是和并行算法以及并行计算机体系结构放在一起讨论的。某个算法在某个机器上的可扩放性反映该算法是否能有效利用不断增加的CPU。我们研究可扩放性的目的就是要使算法尽可能的利用最多的处理器，并且我们也可以预测当某个算法移植到大规模处理机上后的运行效果（即问题规模扩大时对处理器的利用情况）。

Scalability is the capability of a system, network, or process to handle a growing amount of work, or its potential to be enlarged in order to accommodate that growth. For example, it can refer to the capability of a system to increase its total output under an increased load when resources (typically hardware) are added. An analogous meaning is implied when the word is used in an economic context, where scalability of a company implies that the underlying business model offers the potential for economic growth within the company.