Log Reduction Calculator

In February 2026, a food safety technologist emailed asking for clarification on whether a thermal processing step in their protocol achieved the required 5-log reduction for Salmonella. They quoted a temperature of 72°C held for 15 seconds and asked how to verify the log reduction against the regulatory target.

I used this calculator with their starting and target colony counts to show what a 5-log reduction means in practical terms: from 100,000 CFU per gram to 1 CFU per gram, a 99.999% reduction. The FDA HACCP principles guidelines require a minimum 5-log reduction for many ready-to-eat products. Their processing step was documented as exceeding that threshold based on validated thermal inactivation data. The calculator turned an abstract regulatory number into a concrete microorganism count the technologist could use in their HACCP documentation.