The disclosure provides an approach for high-availability admission control. Embodiments include determining a number of slots present on the cluster of hosts. Embodiments include receiving an indication of a number of host failures to tolerate. Embodiments include determining a number of slots that are assigned to existing computing instances on the cluster of hosts. Embodiments include determining an available cluster capacity based on the number of slots present on the cluster of hosts, the number of host failures to tolerate, and the number of slots that are assigned to existing computing instances on the cluster of hosts. Embodiments include determining whether to admit a given computing instance to the cluster of hosts based on the available cluster capacity.