A method and device for determining a tower clearance of a wind turbine. The method includes: acquiring an image of a wind turbine in operation (S10), the image comprising the tips of blades (2) and a tower (1) of the wind turbine; determining the positions of the tips of the blades (2) of the wind turbine in the image acquired (S20); identifying the edges of the tower (1) in the image acquired (30); and calculating, on the basis of the positions of the tips of the blades (2) and the edges of the tower (1) that have been determined, the distance from the tips (2) of the blades (2) to the edges of the tower (1) to acquire a tower clearance (S40).