A new empirical scaling of the magnetic field ratio (the maximum magnetic field on the coil to the toroidal field on the center of helical windings averaged over one field period) for heliotron/torsatron systems has been proposed. This new scaling was derived from the calculation result by using a finite-volume current element code over a wide range of coil engineering parameters. The scaling is described as a product of powers of 5 dimensionless parameters that relate to the coil geometry. This scaling can reproduce the magnetic field ratio within 3% error over the wide range of design parameters. By using this new scaling, we can estimate the magnetic field in the plasma confinement region by a fast calculation with engineering design parameters only. It will facilitate the design optimization through sensitivity analysis with parameter scan over a wide range in reactor design study of heliotron/torsatron reactors.