Konjac glucomannans have been widely considered in health food products although their hydrodynamic properties have been poorly understood. The weight-average molecular weight (Mw); sedimentation coefficient (s020,w) and intrinsic viscosities ([η]) have been estimated for five different preparations. The decrease in both intrinsic viscosity and sedimentation coefficient with molecular weight enables the estimation of molecular flexibility in terms of persistence length (Lp) using the traditional Bohdanecky-Bushin and Yamakawa-Fujii analyses for intrinsic viscosity and sedimentation data respectively. However, this requires an assumption of the mass per unit length ML. Advantage can now be taken of a recent development in data interpretation which allows the estimation of Lp from combined intrinsic viscosity and sedimentation coefficient data and also an estimate for ML. Using this "global" procedure an estimate of (13 ± 1) nm is found for Lp and a value of (330 ± 10) g mol-1 nm-1 for ML.. The value for Lp suggests a molecule of considerable flexibility, comparable to galactomannans (Lp ∼ 8-10 nm) but not as flexible as pullulan (Lp ∼ 1-2 nm).