One of the main challenges in simulating high Reynolds number (italic Re Re) turbulent boundary layers (TBLs) is the long streamwise distance required for large-scale outer-layer structures to develop, making such simulations prohibitively expensive. We propose an inflow generation method for high italic Re Re wall turbulence that leverages the known structure and scaling laws of TBLs. Pre-multiplied spectra of streamwise velocity show that with an increase in italic Re Re the outer region grows and occupies more of the spanwise wavenumber space in proportion to the increase in italic Re Re, while the inner region remains approximately the same. Exploiting this behaviour, we generate inflow conditions for a target italic Re Re by starting from cross-stream velocity slices at a lower base italic Re Re. In spectral space, we identify the inner- and outer-region wavenumbers, and shift the outer-region components proportionally to the desired italic Re Re increase. We examine the capability of this method by scaling velocity slices at italic Re Subscript theta Baseline equals 2240 Reθ=2240 and 4430 to italic Re Subscript theta Baseline equals 8000 Reθ=8000, and using them as inflow conditions for direct numerical simulations of TBLs growing in the range italic Re Subscript theta Baseline equals 8000 minus 9000 Reθ=8000-9000, with italic Re Subscript theta Reθ being the Reynolds number based on the momentum-loss thickness theta θ. The predicted skin friction coefficient and shape factor, regardless of the base italic Re Subscript theta Reθ tested, lie within plus or minus 3.5 percent sign ±3.5% and plus or minus 0.5 percent sign ±0.5%, respectively, of that of a precursor simulation right from the inlet. Reynolds stresses match very well after approximately 8 delta Subscript 99 Sub Subscript 0 8δ990. The development length in terms of the Reynolds stresses is approximately 8 delta Subscript 99 Sub Subscript 0 8δ990, where delta Subscript 99 Sub Subscript 0 δ990 is the boundary layer thickness at the inlet. This gives an order of magnitude reduction in development length compared with other methods proposed in the literature.