Bacterial Half-Life Calculator

∞ generated and posted on 2017.04.17 ∞
∞ updated on 2022.06.05 ∞

The time it takes for half of a bacterial population to become phage adsorbed is easy to calculate as approximately the reciprocal of the product of phage titer and the phage adsorption rate constant.

Please cite as:

Stephen T. Abedon
Bacterial Half-Life Calculator.

Click here for calculator or see immediately below for further explanation and discussion.

For discussion, see:

Abedon, S. T. (2008). Rate of Adsorption is Function of Phage Density (appendix to chapter by L. D. Goodridge: Phages, Bacteria, and Food). In: Bacteriophage Ecology, Abedon, S. T. (ed), Cambridge University Press, Cambridge. pp. 321-324 (of 302-331).

Abedon, S.T. (2022). Further Considerations on How to Improve Phage Therapy Experimentation, Practice, and Reporting: pharmacodynamic perspectives. Phage 3:98-111.

See also: .


Note that bacterial half-life is equal to

-ln(0.5)/([phage adsorption rate constant]×[constant phage titer]),

as rounds up to bacterial mean free time, which is equal to

1/([phage adsorption rate constant]×[constant phage titer])


For discussion of phage adsorption theory, see

For a multiplicity of infection calculator, see

Don't forget to be consistent with your units. Mixing minutes with hours, milliliters with liters, or absolute numbers with concentrations simply will not do! (Regardless, I'm assuming that volumes are in millimeters and time is in minutes.) And if you need a refresher on scientific notation, there is always Wikipedia

= m
above is set to 1 if left blank or not number or ≤ 0
= n
above is set to 0 if left blank or not number or < 0

= m
above is set to 2.5 if left blank or not number or ≤ 0
= n
above is set to -9 if left blank or not number or > 0

k value is defaulted at 2.5 × 10-9 ml-1 min-1 from Stent (1963)
may be greater or lower but must be defined to calculate MOIactual
the larger the number, the faster the phage adsorption