derives mode-mismatch-induced power losses, as a function of mode order, for Hermite-Gauss optical modes. Explicit factors are derived linking mode mismatch losses in a higher order mode to mismatch losses of the fundamental mode. This is particularly relevant for gravitational-wave detectors, where lasers employing higher-order optical modes have been proposed to mitigate thermal noise and quantum-enhanced detectors are very susceptible to losses. This work should inform mode matching and squeezing requirements for Advanced+ and Third Generation detectors.