The pilot reported that during the preflight inspection he was unable to measure the fuel quantity with a dipstick, due to the tailwheel airplane’s tail-low attitude as it sat on the ramp. He stated that he “rocked the wing back and forth…to see the fuel sloshing around” and estimated that the left tank contained 9-10 gallons, and the right tank had “less fuel visible.” The purpose of the flight was to refuel the airplane at the destination airport, where fuel was less expensive. He estimated a fuel burn of 4-5 gallons for the planned 30-minute flight. While enroute, the pilot diverted his course to avoid rain showers that were developing before he ultimately decided to return to the departure airport. During the return, the engine began to “sputter,” at which time he turned on the electric fuel pump and switched the fuel selector from the left tank to the right tank. Sometime after, the engine sputtered again, and he decided to perform an off-airport landing. During landing the airplane struck a fence rail, which resulted in substantial damage to the wings. A post-accident examination of the airplane revealed that the damaged fuel tanks were devoid of fuel, with no indications of fuel having leaked from them, and no odor of fuel was noted at the scene.