Sediment Particle Size Classifier (Wentworth Scale)
Classify sediment particles by the Wentworth scale from diameter.
Includes phi scale and Stokes settling velocity.
Sediment Classification
Wentworth Scale A standard classification system for sediment grain size, ranging from clay (<0.0039 mm) to boulder (>256 mm). Developed by Chester Wentworth in 1922 and still the global standard in sedimentology.
Phi (φ) Scale φ = −log₂(d), where d is diameter in millimetres. The phi scale is logarithmic — each whole unit represents a doubling of grain size. Coarser grains have negative phi values.
Stokes Settling Velocity For fine particles (clay to fine sand), settling velocity in still water: vs = (ρs − ρf) × g × d² / (18 × μ) Using quartz density (2650 kg/m³), water at 20°C (μ = 0.001 Pa·s).