Direct numerical simulations ͑DNSs͒ and experiments of a spatially developing zeropressure-gradient turbulent boundary layer are presented up to Reynolds number Re = 2500, based on momentum thickness and free-stream velocity. For the first time direct comparisons of DNS and experiments of turbulent boundary layers at the same ͑computationally high and experimentally low͒ Re are given, showing excellent agreement in skin friction, mean velocity, and turbulent fluctuations. These results allow for a substantial reduction of the uncertainty of boundary-layer data, and cross validate the numerical setup and experimental technique. The additional insight into the flow provided by DNS clearly shows large-scale turbulent structures, which scale in outer units growing with Re , spanning the whole boundary-layer height.

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