Log Inactivation

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Inputs

Counts mode (N₀ & N) Chick–Watson mode (k·Cⁿ·t)

Initial concentration / count (N₀) i

Example: 1,000,000

Final concentration / count (N) i

Example: 1,000

Optional disinfectant residual (C) i

Optional contact time (t) i

Manual entry is optional. To calculate t, provide the required fields below and click Calculate.

Target log inactivation (required log) i

Kinetic constant for time calc (k) i

Concentration exponent for time calc (n) i

Time calc uses C field above i

Formula (Counts mode): Log Inactivation = log₁₀(N₀ / N).
Optional t calculation (when required log is provided): t = (required log) / (k · Cⁿ).
This keeps the page layout intact while letting you either enter t manually or compute it.

Kinetic constant (k) i

Typical: site/pathogen/disinfectant-specific

Disinfectant residual (C) i

Concentration exponent (n) i

Contact time (t) i

Target log inactivation (required log) i

If t is empty, required log will be used to compute t.

t entry mode i

Formula (Chick–Watson): log₁₀(N₀/N) = k · Cⁿ · t.
Optional t calculation: t = (required log) / (k · Cⁿ) when required log is provided and t is left blank.

Results

Log inactivation

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% reduction

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Reduction ratio (N₀/N)

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CT (C × t)

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Interpretation: —

Index guide (common benchmarks):
• 1-log = 90% reduction
• 2-log = 99% reduction
• 3-log = 99.9% reduction
• 4-log = 99.99% reduction
• 5-log = 99.999% reduction

Note: Regulatory targets vary by jurisdiction, disinfectant, organism, temperature, pH, and water quality.

Analysis and Recomendations

Add notes, findings, and operational recommendations i

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