LOGNORMDIST in ONLYOFFICE: Legacy Lognormal Cumulative Probability

Create DurationModel. Put Parameter in A1 and Value in B1, then enter these values and one formula:

This is an assumed lognormal model for a fictional task duration, not observed data. If X is the duration measured numerically in minutes, ln(X) is modeled as normal with mean μ and standard deviation σ. Use natural logarithms, not base-10 logarithms. The numerical unit must stay consistent when transforming data.

Here exp(μ)=10 is the median, not the arithmetic mean duration. The arithmetic mean is exp(μ+σ²/2), approximately 11.3314845306683 minutes; the mode is exp(μ−σ²), approximately 7.78800783071405. Entering 10 as the mean argument instead of LN(10) specifies a radically different model. A positive skew does not by itself prove real data follow a lognormal distribution.

The official help requires positive x, a mean of ln(x), and a positive standard deviation of ln(x). The function returns the modeled share at or below x. It is not an ordinary normal CDF evaluated at a positive number, and its mean argument is not the arithmetic mean of X.

For the fictional duration model, 10 minutes is the median because its logarithm equals μ. Twenty minutes corresponds to z=(LN(20)−LN(10))/0.5≈1.38629436111989. The normal CDF at that standardized value explains the approximately 91.72% result.

D5 is an interval probability; D6 is the upper tail above 20 minutes. For this continuous model, strict and non-strict endpoint inclusion produce the same areas. That convention differs from a discrete count distribution, where a single endpoint can carry positive probability.

For these positive scalar inputs, =LOGNORM.DIST(B6,B2,B3,TRUE) has the same mathematical target as D4. Include TRUE when moving to the four-argument interface. FALSE requests a density instead, and removing the mode from the modern syntax is not a valid substitution.

The source implementations are separate. LOGNORMDIST requires x>0 and σ>0, but modern LOGNORM.DIST permits nonpositive x in its cumulative branch and returns 0 there. Legacy =LOGNORMDIST(0,LN(10),0.5) is source-predicted #NUM!, not 0. The source also scalarizes explicit array arguments in this legacy path, while the modern class uses array-oriented helpers. These differences justify a separate legacy guide without asserting every client supports a particular spill behavior.

Keep one positive control and one boundary control when comparing a migration. Agreement at 20 minutes alone cannot establish agreement at zero or with array arguments. Preserve the original formula and the exact version alongside any native tests conducted later.

A long right tail is compatible with positive durations, but does not certify that this model fits actual work. Estimate or justify μ and σ from logarithmic data, not from the raw average and raw standard deviation. If the data contain zeros or negative durations, logging them is invalid and may signal a recording or model problem; replacing them silently by an arbitrary small positive value changes the analysis.

The independent identity =NORM.S.DIST((LN(B6)-B2)/B3,TRUE) provides a transformation check for positive inputs. The distribution mean is approximately 11.3314845306683 minutes even though the median is 10. Right skew makes the two unequal. A threshold equal to the arithmetic mean therefore does not generally give a CDF of 0.5.

The implementation uses 0.5+gauss for its normal CDF component. Cancellation can affect tiny left tails, and subtracting a nearly-one CDF can lose a tiny right tail. Do not call a rounded zero an impossible event. Invalid scale and nonpositive x produce numeric errors in the inspected path; nonnumeric conversions can also fail. Error masking should not turn an invalid model into a plausible probability.

Checked October 18, 2026 against current official help and SDKJS tag v10.0.0.169, commit 3679e0375a758d7dc59d31337a45461be3525ed8. Introduction dates and a final supported-version endpoint are not established. Desktop Editors, Docs, mobile releases and imported files require separate compatibility checks.

Neither the ONLYOFFICE application nor its calculation engine was executed for this guide. The numerical targets are independently calculated mathematical values; code-path and error observations are manual source traces. They are not screenshots, displayed workbook results or promises of identical final digits. Use English function names and comma separators as shown, adapting separators to the editor’s locale.

Keep inputs and intermediate probabilities numeric and unrounded. Format the display rather than replacing values with rounded strings. These moderate scalar examples do not certify extreme-tail accuracy, unusual type coercion, array entry or dynamic spill. Model assumptions must be checked separately from arithmetic correctness.

• Official LOGNORMDIST reference, checked October 18, 2026.
• Pinned implementation.
• Pinned normal helpers and beta helper.
• LOGNORM.DIST.
• LOGNORM.INV.
• LOGINV.
• NORM.S.INV and NORM.S.DIST.