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Putting variance into a normal tail formula

A normal VaR or ES coefficient multiplies dispersion in loss units, not variance in squared units.

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Inspect the original model

Mean loss is zero and standard deviation 10 loss units, so variance is 100 squared loss units. Inserting 100 into μ+zσ gives 164.485363 numerically, but that substitutes the wrong risk object and unit.

Restore the correct dispersion

Use σ=10 to obtain 95% VaR 16.448536 and ES 20.627128 loss units. A variance input needs a square root before it can be used as dispersion in these equations.

Check the sum’s compatibility

Unit check
TermUnit
Mean loss μLoss units
z or normal tail multiplierDimensionless
Standard deviation σLoss units
Variance σ²Squared loss units

Keep estimator labels with the data

A data source might report variance, volatility percentage or currency dispersion. Identify and convert the actual quantity rather than relying on a column labeled risk. The calculator expects mean loss and loss standard deviation in the same unit.

Further references