CEC Calculator

Calculate Cation Exchange Capacity and base saturation from clay content, organic matter, and exchangeable cation levels. Evaluate nutrient retention capacity.

Inputs

Clay Content

Organic Matter

Calcium (Ca)

meq/100g

Magnesium (Mg)

meq/100g

Potassium (K)

meq/100g

Tab to move between fields

Results

Estimated CEC

19.5 meq/100g

CEC Rating

High

Base Saturation53.8%

Ca Saturation41%

Mg Saturation10.3%

K Saturation2.6%

Calcium StatusLow

Magnesium StatusOptimal

Potassium StatusOptimal

How to Use This Calculator

Enter your soil texture class or measured clay and organic matter percentages.
Input the CEC value from your soil test report in meq per 100g.
Set your target cation ratios (Ca:Mg, Ca:K).
Review the Cation Saturation percentages for calcium, magnesium, potassium, and hydrogen.
Use the Lime or Gypsum Recommendation output to balance cation ratios for optimal crop uptake.

How the result changes with Clay Content

Clay Content	Estimated CEC	CEC Rating
10	12 meq/100g	Medium
35	24.5 meq/100g	High
65	39.5 meq/100g	Very High
90	52 meq/100g	Very High

What each input means

Clay Content: Percentage of clay in the soil. Clay minerals provide negative charge sites that hold cations.
Organic Matter: Soil organic matter percentage. OM contributes roughly 2 meq/100g per percent.
Calcium (Ca): Exchangeable calcium from soil test report in milliequivalents per 100 grams.
Magnesium (Mg): Exchangeable magnesium from soil test in meq/100g. Ideal is 10–20% of CEC.
Potassium (K): Exchangeable potassium from soil test in meq/100g. Ideal is 2–5% of CEC.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Clay Content = 25, Organic Matter = 3.5, Calcium (Ca) = 8, Magnesium (Mg) = 2 = 5 input(s) provided
Calculate Estimated CEC
Estimated CEC
19.5 = 19.5
Calculate CEC Rating
CEC Rating
High = High
Calculate Base Saturation
Base Saturation
53.8 = 53.8
Calculate Ca Saturation
Ca Saturation
41 = 41

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