Choosing between different organic fertilizers can be difficult. Nutrient ratios, nitrogen (N) availability, ease of use, and cost vary widely between different materials. This fertilizer calculator was developed by OSU and Oregon Tilth using Excel software. It helps farmers compare the cost, nutrient value and nitrogen availability of organic fertilizers. It can help plan a cost effective program that avoids excessive or deficient fertilizer applications. The calculator can be downloaded at no charge from http://smallfarms.oregonstate.edu/ and http://www.tilth.org/Resources/index.html. The calculator has been highlighted in In Good Tilth, Sustaining the Pacific Northwest, and ATTRA's publication Farm Energy Calculators http://attra.ncat.org/energy_calculators.html.