The wavelength, height, and steepness of ripples formed under oscillat
ory flows in flume and field studies are reexamined to construct a sim
ple and accurate method of predicting these ripple properties. Ripples
with wavelengths proportional to near-bed wave orbital diameter (orbi
tal ripples), predominant in laboratory experiments, are found to have
heights in excess of the thickness of the wave boundary layer. Ripple
s with wavelengths that are roughly proportional to grain size and nea
rly independent of orbital diameter (anorbital ripples), which predomi
nate in the field, have heights at least several times smaller than wa
ve boundary layer thickness. Relating wave boundary layer height to th
e generally more easily estimated wave orbital diameter, a set of expr
essions are developed for predicting ripple type and geometry based on
mean grain size, wave orbital diameter, and estimated anorbital rippl
e height. This method provides a good characterization of ripple wavel
ength and steepness for a large set of combined field and flume data.