What is the Pooled Standard Deviation Calculator?
Combine two sample standard deviations into a pooled estimate. ITS Research Solution keeps the interactive tool above the explanation so you can calculate first and then review the method used.
Formula or method
Pooled SD = √[((n1−1)s1² + (n2−1)s2²) / (n1+n2−2)].
How to use this tool
Enter the requested values using consistent units, run the calculation and review the main result plus any supporting values. Two groups can be combined when a common-variance estimate is appropriate.
Interpretation and limitations
Do not use a pooled-variance approach when equal variance is not a reasonable assumption. Always check source data, units, rounding and discipline-specific requirements before using a result in assessed, published, regulated or high-stakes work.
Frequently asked questions
How is this result calculated?
Pooled SD = u221a[((n1u22121)s1u00b2 + (n2u22121)s2u00b2) / (n1+n2u22122)].
Can I use this result in formal academic or research work?
Use it as a transparent calculation aid, then verify the assumptions, units, rounding and any institution-, journal- or field-specific requirements before formal use.