SBZ Corp. recently developed a free iPhone- and Blackberry-compatible SBZ Converter app for volume-to-weight calculations, because in order to mathematically convert between volume and weight, density has to be factored into the calculation. The SBZ Converter offers:
- A portable conversion tool that enables people to convert between any units quickly and accurately, whether it be from volume to weight, weight to volume, volume to volume or weight to weight.
- Ideal suitability for industries handling liquids because units of measure are commonly referred to in both weight and volume, such as metric tons, cubic meters, kilos, liters, barrels, gallons and pounds.
- Freedom from a contract, signing up and long information-gathering forms to complete.
iPhone users: http://itunes.apple.com/gb/app/sbz-convert/id377387102?mt=8 
Blackberry users: www.sbzcorporation.com/blackberry-app.php