Animal Manure Calculations
Adapted in part from NCSU Type A AWMS Certification Program



Useful Abbreviations

ppm = parts per million = milligrams/liter (mg/l)
PAN = plant-available nitrogen

Conversion Factors


P (lbs) P2O5 (lbs) K (lbs) K2O (lbs)

ppm lb/1000 gal lb/ton lb/bu % (liquid)

cubic feet gallons

cubic feet tons (solid)

tons bushels  

lbs bushels  

bushels (solid) cubic feet  
Acre-inches and Gallons
Acre-inches Gallons  
Acres and Square Feet
Acres Square feet  

Important Formulas



1. Acres needed for manure application  (Enter any two values to calculate the third value.)
gal (or tons) of manure produced annually manure application rate gal (or tons) / acre Acres needed for waste application
2. Application Rate (gallons per acre)  (Enter any two values to calculate the third value.)
crop PAN requirement (lb) / acre lb PAN / 1000 gal Application rate (gal/acre)
3. Application Rate (tons per acre)  (Enter any two values to calculate the third value.)
crop PAN requirement (lb/ac) lb PAN / ton (from waste analysis) Application Rate Needed (tons/acre)
4. Pound of plant-available nitrogen applied per acre  (Enter any two values to calculate the third value.)
application rate (gal) of waste applied / acre lb PAN / 1000 gal Application rate (lb PAN/acre)
5. Area of a rectangle
length (ft) width (ft) Area (ft2) Area (Acres)
5. Area of a circle
radius (ft) Area of circle (ft2)
6. Coverage Area and Application Rate for Spreader
Spreader load volume (gal) or weight (tons) length (ft) width (ft) Coverage area (acres) Application rate for spreader (gal or tons/acre)

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