The pilot reported that, prior to departure, he was told the helicopter was topped off with fuel for the multi-stop flight. He added that he did not verify the fuel quantity. During the last leg, he departed about 60 miles from the destination airport with just below 600 pounds of fuel and he decided to fly at 120 knots with a tailwind. He added that about 3 miles from the destination airport, the engine lost power. He performed an autorotation but landed hard. The pilot reported that after landing, the fuel quantity gauge read about 225 pounds of fuel remaining and that the 20-minute fuel light which did not illuminate during the flight, illuminated once on the ground. The pilot was unsure if anyone had verified the fuel quantity remaining after landing, but they added about 50 gallons of fuel and continued to the destination airport. He estimated that the helicopter's fuel burn was about 75 to 80 gallons/hour. The chief pilot and owner reported that he had refueled the helicopter, which was on uneven terrain, before the flight. He filled the tank to the bottom of the filler cap on the left side, which he estimated was about 10 to 15 gallons less than total fuel capacity of 210 gallon tank. He estimated that the helicopter burned about 90 gallons/hour. He added that there were no open mechanical squawks on the helicopter and that he was not aware of any mechanical issues. The Federal Aviation Administrator inspector, who examined the helicopter at the accident site, reported that the fuel quantity gauge had been serviced and calibrated earlier in the year, but continued to indicate fuel after the helicopter ran out of fuel. The 20-minute low fuel light appeared to be functioning normally. The helicopter sustained substantial damage to the tailboom and transmission mounts. The pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation.