# Conversion Factors Needed for Common Fertilizer Calculations

### ID

SPES-201NP

## Introduction

The world is a big place and farmers, industry, government, and others likely use different units, oxidation states, and measurements when calculating and reporting nutrient use for farming systems. The following table outlines some of the most common conversions needed for nutrient management. For instance, to convert K to K_{2}O, you would multiply your K number by 1.2051. So, a fertilizer being reported as 49.8% K is also commonly reported as 49.8% × 1.2051 = 60% K_{2}O. Therefore, you are equally correct to report muriate of potash (KCl) fertilizer as 49.8% K or 60% K_{2}O, as long as you have the correct unit represented. However, note that fertilizer law generally states that certain oxidation states should be reported for certain nutrients (i.e. K_{2}O must be used on Virginia fertilizer labels).

Column 1: Conversion | Multiply by | Column 2: Multiplication Value |
---|---|---|

P to P_{2}O_{5} |
Multiply P by | 2.2910 |

P_{2}O_{5} to P |
Multiply P_{2}O_{5} by |
0.4365 |

K to K_{2}O |
Multiply K by | 1.2051 |

K_{2}O to K |
Multiply K_{2}O by |
0.8301 |

KCl to K | Multiple KCl by | 0.5244 |

KCl to Cl | Multiply KCl by | 0.4756 |

K_{2}SO_{4} to K |
Multiply K_{2}SO_{4} by |
0.4487 |

Mg to MgO | Multiply Mg by | 1.6578 |

MgO to Mg | Multiply MgO by | 0.6032 |

MgCO_{3} to MgO |
Multiply MgCO_{3} by |
0.4782 |

MgO to MgCO_{3} |
Multiply MgO by | 2.0913 |

MgSO_{4} to Mg |
Multiply MgSO_{4} by |
0.2020 |

MgCO_{3} to CaCO_{3} |
Multiply MgCO_{3} by |
1.1867 |

CaO to Ca | Multiply CaO by | 0.7147 |

Ca to CaO | Multiply Ca by | 1.3992 |

CaCO_{3} to MgCO_{3} |
Multiply CaCO_{3} by |
0.8426 |

CaCO_{3} to CaO |
Multiply CaCO_{3} by |
0.5603 |

K_{2}SO_{4} to S |
Multiply K_{2}SO_{4} by |
0.1840 |

CaSO_{4 }to Ca |
Multiply CaSO_{4} by |
0.2938 |

CaSO_{4} to S |
Multiply CaSO_{4} by |
0.2350 |

SO_{4} to S |
Multiply SO_{4} by |
0.3339 |

S to SO_{4} |
Multiply S by | 2.9963 |

NaCl to Cl | Multiply NaCl by | 0.6066 |

N to NH_{3} |
Multiply N by | 1.2158 |

N to KNO_{3} |
Multiply N by | 7.2162 |

NH_{3} to N |
Multiply NH_{3} by |
0.8225 |

N to (NH_{4})_{2}SO_{4} |
Multiply N by | 4.7160 |

(NH_{4})_{2}SO_{4} to N |
Multiply (NH_{4})_{2}SO_{4} by |
0.2120 |

(NH_{4})_{2}SO_{4} to S |
Multiply (NH_{4})_{2}SO_{4} by |
0.2427 |

N to NH_{4}NO_{3} |
Multiply N by | 2.8571 |

NH_{4}NO_{3} to N |
Multiply NH_{4}NO_{3} by |
0.3500 |

Column 1: Conversion | Multiply by | Column 2: Multiplication Value |
---|---|---|

Parts per million (ppm) to pounds per acre (lbs./acre) | Multiply ppm by | 2.0 |

Pounds per acre (lbs./acre) to parts per million (ppm) | Multiply lbs./acre by | 0.5 |

Percent to gram per kilogram | Multiply percent by | 10 |

Gram per kilogram to percent | Multiply gram per kilogram by | 0.1 |

Column 1: Conversion | Multiply by | Column 2: Multiplication Value |
---|---|---|

Mile to kilometer | Multiply mile by | 1.609 |

Kilometer to mile | Multiply kilometer by | 0.621 |

Foot to meter | Multiply foot by | 0.304 |

Meter to foot | Multiply meter by | 3.28 |

Column 1: Conversion | Multiply by | Column 2: Multiplication Value |
---|---|---|

Acre to hectare | Multiply acre by | 0.405 |

Hectare to acre | Multiply hectare by | 2.47 |

Square foot to square meter | Multiply square foot by | 0.0929 |

Square meter to square foot | Multiply square meter by | 10.76 |

Column 1: Conversion | Multiply by | Column 2: Multiplication Value |
---|---|---|

Gallon to liter | Multiply gallon by | 3.78 |

Liter to gallon | Multiply liter by | 0.265 |

Quart to liter | Multiply quart by | 0.946 |

Liter to quart | Multiply liter by | 1.057 |

Column 1: Conversion | Multiply by | Column 2: Multiplication Value |
---|---|---|

Pound to gram | Multiply pound by | 454 |

Gram to pound | Multiply gram by | 0.00220 |

Pound to kilogram | Multiply pound by | 0.454 |

Kilogram to pound | Multiply kilogram by | 2.205 |

U.S. ton to tonne | Multiply U.S. ton by | 0.907 |

Tonne to U.S. ton | Multiply tonne by | 1.102 |

Column 1: Conversion | Multiply by | Column 2: Multiplication Value |
---|---|---|

Pound per acre to kilogram per hectare | Multiply pound per acre by | 1.12 |

Kilogram per hectare to pound per acre | Multiply pound per acre by | 0.893 |

Bushel per acre (bu/acre) for 60 lb. bushel to kilogram per hectare | Multiply pound per acre by | 67.19 |

Bushel per acre (bu/acre) for 56 lb. bushel to kilogram per hectare | Multiply bu/acre by | 62.71 |

Bushel per acre (bu/acre) for 48 lb. bushel to kilogram per hectare | Multiply bu/acre by | 53.75 |

Gallon per acre to liter per hectare | Multiply gallon per acre by | 9.35 |

Liter per hectare to gallon per acre | Multiply liter per hectare by | 0.107 |

Column 1: Conversion | Multiply by | Column 2: Multiplication Value |
---|---|---|

Fahrenheit (°F) to Celsius (°C) | Multiply Fahrenheit by | 5/9 × (°F - 32) |

Celsius (°C) to Fahrenheit (°F) | Multiply Celsius by | (9/5 × °C) + 32 |

## References

Alley, M.M. 2000. “Part VIII: Fertilizers.” *Agronomy Handbook*. Publication 424-100. Virginia Cooperative Extension, Blacksburg.

American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 2020. “Chapter 7: Units and Measurements.” *Publications Handbook & Style Manuel. *Madison, WI.

## Acknowledgements

Funding for this work was provided in part by the Virginia Agricultural Experiment Station and the Hatch program of the National Institute of Food and Agriculture, US Department of Agriculture.

*Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.*

*Virginia Cooperative Extension is a partnership of Virginia Tech, Virginia State University, the U.S. Department of Agriculture, and local governments. Its programs and employment are open to all, regardless of age, color, disability, sex (including pregnancy), gender, gender identity, gender expression, genetic information, ethnicity or national origin, political affiliation, race, religion, sexual orientation, or military status, or any other basis protected by law.*

### Publication Date

April 29, 2020