Log Reduction

Measure the efficacy of disinfection or sterilization processes by calculating log and percent reduction of microbes.

Microbial Counts

Initial Count (CFU/mL)

Final Count (CFU/mL)

Reduction Efficacy

Enter counts to see efficacy

Quick Reference

1-Log90% Reduction

2-Log99% Reduction

3-Log99.9% Reduction

4-Log99.99% Reduction

5-Log99.999% Reduction

6-Log99.9999% Reduction

Overview

Log reduction is a mathematical term used to express the relative number of living microbes eliminated by a disinfection process.

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Pro Tips

A 1-log reduction means 90% of microbes have been eliminated.
High-level disinfection usually requires at least a 6-log reduction.
CFU stands for Colony Forming Units, a measure of viable microbial cells.

Fun Facts

"A 6-log reduction (99.9999%) is considered 'sterility' for medical devices."
"Hand sanitizers often claim 99.9% effectiveness, which is a 3-log reduction."
"The 'PNSU' (Probability of a Non-Sterile Unit) for sterile items is typically 10⁻⁶."
"Bacterial spores are the hardest to kill, often used as biological indicators."

Formula: Log Reduction = log₁₀(N₀ / Nₜ)

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