Tidal measurements are subject to various errors. Because of the increasing emphasis on the accuracy of the data obtained by the Tide and National Water Level Network, the knowledge of these errors is of great importance. This paper summarizes the development of error models pertinent to tide measurement systems utilizing stilling wells and floats. The major error sources addressed include wind waves, water currents, float response, water density variation and marine fouling. Laboratory experiments including a wave tank, tow tank, and oscillatory water tunnel tests were also conducted to validate the wave, current and float response models. The error models developed can be useful tools for evaluating tide measurement systems utilizing stilling wells and floats and can also provide guidance to future design modifications to reduce tidal measurement errors.