Log Reduction Calculator

Formula

To calculate the Log Reduction:

\[ \text{Log Reduction} = \log \left( \frac{A}{B} \right) \]

To calculate the Percent Reduction:

\[ \text{Percent Reduction} = \left( \frac{A - B}{A} \right) \times 100 \]

Where:

\( A \) is the number of viable microorganisms before treatment
\( B \) is the number of viable microorganisms after treatment

What is a Log Reduction?

A log reduction is a simplified way of showing the reduction in microorganisms before and after treatment. Using logs is useful because it reduces very large numbers to something manageable.

Example Calculation 1

Let's assume the following values:

Number of Viable Microorganisms Before Treatment \( A \) = 1,000,000
Number of Viable Microorganisms After Treatment \( B \) = 1,000

Step 1: Calculate the log reduction:

\[ \text{Log Reduction} = \log \left( \frac{1,000,000}{1,000} \right) = \log (1,000) = 3 \]

Step 2: Calculate the percent reduction:

\[ \text{Percent Reduction} = \left( \frac{1,000,000 - 1,000}{1,000,000} \right) \times 100 = 99.9 \% \]

So, the Log Reduction is 3 and the Percent Reduction is 99.9%.

Example Calculation 2

Let's assume the following values:

Number of Viable Microorganisms Before Treatment \( A \) = 500,000
Number of Viable Microorganisms After Treatment \( B \) = 50,000

Step 1: Calculate the log reduction:

\[ \text{Log Reduction} = \log \left( \frac{500,000}{50,000} \right) = \log (10) = 1 \]

Step 2: Calculate the percent reduction:

\[ \text{Percent Reduction} = \left( \frac{500,000 - 50,000}{500,000} \right) \times 100 = 90 \% \]

So, the Log Reduction is 1 and the Percent Reduction is 90%.