The plt reported that he preflighted the acft & decided there was sufficient fuel to haul skydivers on 2 more flts. On the 2nd flt, he had to make three passes instead of one. During the apch to the arpt, the eng lost power from fuel exhaustion. The plt tried to reach the rwy, but landed short on plowed terrain. The wheels dug into the plowed terrain, the nose gear collapsed & the acft nosed over. The plt had planned a fuel consumption rate of 12.1 gal/hr. However, the actual fuel consumption (after installation of a new eng) was 12.8 gal/hr.