Pretty close (close enough!) - Mr Wikipedia says "24 AWG (0.51054 mm diameter; 0.205 mm²2 CSA)".100mΩ/m is 100/18.3 = 5.46 x that of 1mm², therefore the wire must be 1/5.46 = 0.183mm² csa and 0.483mm. in diameter. Is that about the size of Cat5.
Kind Regards, John