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NORMINV Function

Excel 2007+

Summary

The NORMINV function calculates the inverse of the normal cumulative distribution, returning the value corresponding to a given probability within a normal distribution defined by its mean and standard deviation. This legacy function finds the x-value where the cumulative distribution function equals the specified probability.

Syntax

NORMINV(probability, mean, standard_dev)

Parameters

Parameter	Type	Required	Description
probability	`Number`	Yes	A probability value from 0 (exclusive) to 1 (exclusive)
mean	`Number`	Yes	The expected average value of the distribution
standard_dev	`Number`	Yes	The standard deviation (must be positive)

Using the NORMINV Function

NORMINV is essential for statistical analysis when you need to find specific values within a normal distribution based on probability thresholds. Use it for determining critical values, setting confidence intervals, or converting probabilities to actual data points in normally distributed datasets.

Common NORMINV Examples

Basic NORMINV Calculation

=NORMINV(0.908789, 40, 1.5)

Returns approximately 42, the value where 90.88% of values fall below in a normal distribution with mean 40 and std dev 1.5

Confidence Interval Boundary

=NORMINV(0.975, 100, 15)

Finds the value exceeded by only 2.5% of observations (97.5th percentile)

Standard Normal (Z-score)

=NORMINV(0.95, 0, 1)

Returns the Z-score for 95% probability (approximately 1.645)

Frequently Asked Questions

NORMINV returns #NUM! error if probability ≤ 0 or ≥ 1.

NORMINV is the legacy version. NORM.INV offers improved accuracy and is recommended for new formulas.

Returns #NUM! error value.

Common Errors and Solutions

#VALUE!

Cause: Any argument is non-numeric

Solution: Ensure all inputs are valid numbers

#NUM!

Cause: Probability ≤ 0 or ≥ 1, or standard_dev ≤ 0

Solution: Use probability between 0 and 1 exclusively, positive standard deviation

#N/A

Cause: Iterative search failed to converge after 100 iterations

Solution: Check input precision or use NORM.INV instead

Notes

Legacy function - consider NORM.INV for better accuracy
Uses iterative algorithm that may occasionally fail to converge
When mean=0 and standard_dev=1, equivalent to NORMSINV
Precision depends on NORMDIST function accuracy

Compatibility

Available in: Excel 2007, Excel 2010, Excel 2013, Excel 2016, Excel 2019, Excel 2021, Microsoft 365

Not available in: Excel 2003 and earlier

Content last reviewed: December 9, 2025
Update frequency: As needed
Excel versions tested: Excel 2007+