Log Reduction Requirement Calculator

Work out log reduction requirement instantly with clear inputs, formula shown and shareable results.

About Log Reduction Requirement Calculator

Required log reduction is log10 of initial load divided by acceptable load, plus a safety margin. Each log is a tenfold reduction, so going from 10^5 to 0.1 CFU/g needs 6 logs. Comparing that with the reduction the process actually delivers shows whether the process is adequate.

Formulas

Log reduction

Required logs = log10(initial load / acceptable load) + safety margin

Survivors

Survivors = initial load x 10^(-delivered logs)

Worked example

With the default values below, Log Reduction Requirement Calculator returns Log Reduction Required of 7.0000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Initial Loadminimum 0 CFU/g: 100,000 CFU/g
Acceptable Final Loadminimum 0 CFU/g: 0.1 CFU/g
Additional Safety Marginminimum 0 log: 1 log
Log Reduction Delivered By Processminimum 0 log: 5 log

Results

Log Reduction Required: 7.0000
Shortfall Against Process: 2.0000
Predicted Survivors: 1.00000000
Process Adequacy: Process inadequate - increase lethality

Step by step

1Values used
2Log reduction
3Survivors
4Log Reduction Required= 7.0000
5Shortfall Against Process= 2.0000
6Predicted Survivors= 1.00000000
7Process Adequacy= Process inadequate - increase lethality

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or compounding frequency into account.
Figures are rounded for display to 8 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Required log reductions for pathogen control are set by regulation and must be validated for the specific product and process, not assumed.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Required log reductions for pathogen control are set by regulation and must be validated for the specific product and process, not assumed.

Frequently Asked Questions

What log reduction do common processes deliver?

Pasteurisation of milk gives 5 or more logs of vegetative pathogens; a chlorine wash on produce gives only 1-2 logs; high pressure processing 5-6 logs depending on product and pathogen.

Why add a safety margin?

To cover variability in initial load, process delivery and organism resistance. Regulations often specify the required reduction directly, and that specification takes precedence.