The force exerted by electromagnetic fields is of fundamental importance in physics. Intense debates on the conventionally accepted Lorentz formulation and the recently suggested Einstein–Laub formulation still continue due to lack of experimental evidences. To distinguish these two formulations, we experimentally investigated the topological charge of optical force in a solid dielectric, and found that the force exerted by a Gaussian beam has components with topological charge of both 2 and 0, which agrees with neither the Lorentz nor Einstein–Laub formulation. Instead, we found a modified Helmholtz theory could explain our experimental results. This work not only contributes to the ultimate determination of the correct force formulation in classical electrodynamics, but also has broad and far-reaching impact on many subjects involving electromagnetic forces.