How this calculator works
RSD divides standard deviation by the absolute arithmetic mean and displays the ratio as a percentage. Raw-data mode permits the n - 1 sample divisor or n population divisor. Unlike signed coefficient of variation, a negative mean does not produce a negative RSD. Comparisons are most useful for measurements with a meaningful zero and become unstable as the mean approaches zero.
Formula
RSD (%) = 100 × SD/|mean|.
Worked example
A mean of -20 and standard deviation of 4 give RSD = 100 × 4/20 = 20%. For population observations 2 and 4, mean is 3, SD is 1 and RSD is 33.333333%.
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Frequently asked questions
How does this differ from signed CV?
RSD uses the magnitude of the mean and is expressed as a non-negative percentage. Signed CV retains the mean sign as a ratio.
Can RSD exceed 100%?
Yes. Standard deviation can be larger than the magnitude of the mean. There is no general upper bound.
Is this the relative standard error?
No. RSD describes observation spread; relative standard error describes uncertainty in an estimated statistic.