List the values
Calculate the mean
Subtract the mean from each value
Square each difference
Add the squared differences
Divide by n for population standard deviation
Divide by n – 1 for sample standard deviation
Take the square root of the result
Use the formula: STDEV = sqrt(Σ(x – mean)² / (n – 1)) for sample data
Use the formula: STDEV = sqrt(Σ(x – mean)² / n) for population data