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Both calculators run independently — change the inputs on either side to compare results.

Normal Distribution Probability Calculator

Calculate the probability that a normally distributed random variable falls within a specified range, below a threshold, or above one — using the mean and standard deviation that fully describe the bell curve. Used for Six Sigma quality control, finance (VaR), psychometrics, and any process modelled by the normal distribution.

Mean (μ)

Standard Deviation (σ)

Lower Bound

Upper Bound

Fill in the required fields to see your result.

Probability

Confidence Interval Calculator

Computes the range of values likely to contain a true population mean at your chosen confidence level. Use it when reporting survey results, clinical trial outcomes, or any estimate derived from a sample.

Sample Mean

Sample Standard Deviation

Sample Size (n) (observations)

Confidence Level

Distribution Type

Fill in the required fields to see your result.

Key differences

	Normal Distribution Probability Calculator	Confidence Interval Calculator
Category	Statistics	Probability
Inputs required	4	5
Result	Probability	Margin of Error (±)
What it does	Calculate the probability that a normally distributed random variable falls within a specified range, below a threshold, or above one — using the mean and standard deviation that fully describe the bell curve. Used for Six Sigma quality control, finance (VaR), psychometrics, and any process modelled by the normal distribution.	Computes the range of values likely to contain a true population mean at your chosen confidence level. Use it when reporting survey results, clinical trial outcomes, or any estimate derived from a sample.