Complex sentence: The large Russian SS-18 ICBM has a payload capacity of 7200 kg, so the calculated maximum delivered yield would be 37.4 megatons of TNT and a Saturn V scale missile could deliver over 120 tons with a yield of about 700 megatons.
Split into simpler sentences: The large Russian SS-18 ICBM has a payload capacity of 7,200 kg, so the calculated maximum delivered yield would be 37.4 megatons of TNT. A Saturn V-scale missile, if constructed, could deliver over 120 tons with a yield of about 700 megatons.