Convert your density to lb/yd3. 100 lb/ft3= 2700 lb/yd3(1 pound per cubic foot equals 27 pounds per cubic yard) If you're in the US, divide 2700 by 2000 (there are 2000lb in a US ton). If you're in the UK, divide by 2200 (there are 2204.62 lb in a metric tonne) ...