The direct measurement of wall shear stress in turbulent boundary layers (TBL) is challenging, therefore requiring it to be indirectly determined from mean profile measurements. Most popular methods assume the mean streamwise velocity to satisfy either a logarithmic law in the inner layer or a composite velocity profile with many tuned constants for the entire TBL, and require reliable data from the noise-prone inner layer. A simple method is proposed to determine the wall shear stress in zero pressure gradient TBL from measured mean profiles, without requiring noise-prone near-wall data. The method requires a single point measurement of mean streamwise velocity and mean shear stress in the outer layer, preferably between $20$ to $50$ $%$ of the TBL, and an estimate of boundary layer thickness and shape factor. The friction velocities obtained using the proposed method agree with reference values, to within $3$ $%$ over a range of Reynolds number.
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