Sediment transport capacity is an important control on soil erosion and deposition by overland flow. To investigate the controls of transport capacity in laminar interrill overland flow on stone‐covered surfaces, 357 flume experiments were performed using a single sediment size. Multiple regression analyses reveal that transport capacity is positively related to excess flow power ω − ω_c, but the slope of the relation is steeper where ω < 0.3 W m⁻² than where ω ≥ 0.3 W m⁻². Transport capacity is positively related to rainfall intensity where ω < 0.3 W m⁻² and negatively related to rainfall intensity where ω ≥ 0.3 W m⁻². Transport capacity is negatively related to stone concentration and positively related to stone size irrespective of the value of ω. Finally, transport capacity is negatively related to fluid viscosity where ω < 0.3 W m⁻² and unrelated to viscosity where ω ≥ 0.3 W m⁻².