A determination of the steady state nucleation rate r(n) in thermally annealed a-Si:H has typically been performed using TEM, where the increase in grain density with isothermal sample anneal time can be directly observed for samples with small crystalline volume fractions. Using the classical model of crystallite nucleation and grain growth, this paper presents an alternative technique for determining rn using in situ XRD measurements of the crystallization time and EBSD measurements of the final grain size, the latter in fully annealed samples. HWCVD a-Si:H samples containing different as-grown film H contents C(H) have been examined by both techniques, and the agreement between these techniques is excellent. R(n) is seen to decrease with increasing as-grown film C(H). Differences in the values of r(n) are suggested as being due to variations in the transition rate per atom at the amorphous/crystalline interface. Published by Elsevier B.V.