Ratio of the scale-dependent matter growth rate f(k, z) in f(R) gravity (for the fiducial value |f_R0| = 5 × 10⁻⁶) with respect to ΛCDM for three different wavenumbers, 5 × 10⁻³ (solid blue line), 5 × 10⁻² (dashed purple line), and 5 × 10⁻¹ h Mpc⁻¹ (dot-dashed orange line), as a function of redshift from z = 0 to z = 2.5. The smaller the spatial scales and the lower the redshifts, the larger the enhancement of the growth rate compared to ΛCDM.