Please visit GiveWell.org This CharityScorecard.org site was in use from 2006 to 2008, but is now mostly dormant, and the material here is out of date. The GiveWell project has similar goals and is being actively maintained. I've left the old CharityScorecard.org content here just for the historical record.

From CharityScorecard

Benefit-Cost Ratio (BCR) 

Once a CBA is done, the resulting BCR is calculated as the total benefits divided by the total costs. The BCR will be a unitless number, like "0.26", or "4.25". The bigger the BCR, the more cost-effective the project is. If the BCR is greater than 1.0, then the benefits outweigh the costs, and the project is cost-effective. If the BCR is less than one, then the costs outweigh the benefits, and the project is not cost-effective.