Free · Laboratory calculations

Observed Mutant Fraction of a Population

Calculate observed mutant frequency from mutant and total counts, or recover a count from the fraction.

Calculator inputs

Loading calculator…

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

20 mutant cells among 10,000 total cells give a mutant fraction of 0.002, equivalent to 0.2%.

Observed mutant fraction = mutant count / total population count

Enter these known values and leave the other values blank.

Counts are nonnegative and the total count is positive. Mutants are a subset of the total, so their count cannot exceed it.
Use comparable population counts or estimates on the same basis. An inverse calculation may return a fractional expected count; actual counted cells are whole numbers.
The output is a fraction, not a percentage: multiply by 100 for percent. Zero observed mutants is allowed.
Observed frequency is not the probability of mutation per cell division. Estimating a mutation rate requires an appropriate experimental and statistical model.

No. As a fraction, 0.002 equals 0.2 percent or 2 per 1,000.

No. It describes the observed sample. It does not establish a zero mutation rate or account for detection limits.

Bookify permits zero observed mutants and requires the mutant count to be no greater than the total population.