Enter the number of viable microorganisms before treatment and after treatment into the calculator to determine the log reduction and percent reduction.
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Log Reduction Formula
The following formula is used to calculate a log reduction.
Log Reduction = log10 (A/B)
Percent Reduction = (A-B) * 100 / A
- Where A is the number of viable microorganisms before treatment.
- B is the number of viable microorganisms after treatment.
Log Reduction Definition
What is a log reduction? A log reduction is a simplified way of showing the reduction in microorganisms before and after a treatment. Using logs is useful because it reduces very large numbers to something manageable.
How to perform log reduction?
- First, determine the number of microorganisms before treatment.
For this example, this value is 2,000,000.
- Next, determine the number of microorganisms after treatment.
After treatment there are only 500 microorganisms left.
- Finally, calculate the log reduction.
The log reduction is found to be: log10 ( A/B ) = 3.602.
About Log Reduction
Can a log reduction be negative? If the number of microorganisms increases after treatment, the resulting log reduction will be negative. This means that there was actually an increase as opposed to a reduction, hence the negative value.
What does 3 log reduction mean? A 3 log reduction is equivalent to a 99.99% reduction in quantity, which in this case is quantity of microorganisms.
What is 6 log reduction? A 6 log reduction is equivalent to a 99.9999% reduction in a quantity.
What is 5 log reduction? A 5 log reduction is equal to 99.999% reduction.
What is 4 log reduction? A 4 log reduction is equal to 99.99% reduction.
What is 2 log reduction? A 2 log reduction is equal to 99% reduction.
What is 1 log reduction? A 1 log reduction is equal to 90% reduction.