The normal distribution (bell curve) is the most widely used probability distribution.
68% of data falls within 1 standard deviation of the mean.
Reach for this calculator when you need a result you can act on confidently. The formula is straightforward, but manual computation introduces rounding errors that this tool eliminates entirely.
The most frequent error is rounding intermediate values before completing the full calculation. Round only the final result — rounding intermediate steps compounds errors in multi-step calculations, sometimes significantly.
A business owner spots that revenue grew from £180,000 last year to £213,400 this year. The calculator confirms the increase is 18.6% — a figure needed for the annual report and for comparing against the industry growth rate cited in the sector report.
A symmetric bell-shaped distribution defined by mean μ and standard deviation σ.
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