EXPON.DIST in Collabora Office: Model Waiting Times With an Explicit Rate
Use Collabora EXPON.DIST to distinguish exponential density, cumulative probability and survival, with reproducible waiting-time examples.
Verification status: See the evidence and test scope described in this guide. How formula examples are checked
Quick answer: =EXPON.DIST(3;0.5;1) has independently expected result approximately 0.776869840. In an exponential waiting-time model with rate 0.5 per time unit, it is the probability of waiting no more than three time units.
Syntax and units
=EXPON.DIST(Number; Lambda; C)
Number is the time or other nonnegative quantity being evaluated. Lambda is the positive rate parameter. C selects the form: the dedicated Collabora help specifies zero for density and one for cumulative distribution. Supply all three arguments and use an explicit zero or one.
The independent mathematical definitions are density Lambda*EXP(-Lambda*Number) and cumulative probability 1-EXP(-Lambda*Number). Lambda has reciprocal units: a rate per hour must be paired with a time in hours. The mean waiting time is 1/Lambda, so a mean of two hours corresponds to Lambda=0.5 per hour.
The model assumes a constant event rate and the appropriate independent-event process. A waiting-time function does not establish those assumptions from your observations. The following numbers illustrate the distribution, not a forecast about any real service.
Example 1: compare cumulative probabilities and densities
Put 0, 1, 2, 3, 4, 6 in A2:A7. Put 0.5 in F2 as the rate per hour. In B2 enter =EXPON.DIST(A2;$F$2;1) and fill down. The independent targets are approximately 0, 0.393469340, 0.632120559, 0.776869840, 0.864664717, 0.950212932.
In C2 enter =EXPON.DIST(A2;$F$2;0) and fill down. At three hours the density is approximately 0.111565080, whereas the cumulative probability is approximately 0.776869840. Label the columns “Probability by time” and “Density per hour.” A density is not the probability of an exact continuous waiting time.
The value at zero is also a useful distinction: the independent cumulative target is zero, while the density target is 0.5. Those values are compatible because one is an accumulated area and the other is a curve height.
Example 2: calculate a waiting-time band
The event “between two and four hours” has probability =EXPON.DIST(4;0.5;1)-EXPON.DIST(2;0.5;1), independently approximately 0.232544158. Subtract cumulative values, not densities.
The event “longer than four hours” uses =1-EXPON.DIST(4;0.5;1), independently approximately 0.135335283. Together with the probability through four hours, this should total one apart from numerical rounding.
For a continuous model, assigning an endpoint to either neighboring interval does not change its probability. That differs from a discrete count model where an exact count can have positive probability.
Advanced application: derive a percentile without an inverse function
For a probability p strictly between zero and one, the exponential quantile is =-LN(1-p)/Lambda. With p=0.5 and Lambda=0.5, the median is approximately 1.386294361 hours. With p=0.95, the target is approximately 5.991464547 hours.
Put 0.95 in F4 and use =-LN(1-F4)/F2 in F5. Checking =EXPON.DIST(F5;F2;1) should target F4. Keep the unrounded F5 value for this round trip.
The median differs from the two-hour mean. For this right-skewed distribution, the 50th-percentile threshold is below the mean waiting time; using “average” as a synonym for “50th percentile” would give the wrong threshold.
Errors and troubleshooting
Validate a numeric nonnegative Number and positive Lambda for this model. The brief dedicated help does not specify every invalid-input code, text coercion or extreme-tail numerical behavior, and none is certified here.
Check rate-versus-mean confusion first if results look wrong. With minutes instead of hours, a half-per-hour rate is 0.5/60 per minute; 180 minutes then matches three hours. Large-tail complements can lose numerical precision, so validate critical tail calculations in the actual application.
Availability and verification
The exact function is documented in Collabora Office 26.04 desktop help. Its source snapshot was retrieved on 2026-10-13 and hash-verified for this guide on October 15, 2026. Desktop documentation is not proof of Online or mobile support.
First introduced release and last functioning version are unknown. The available dedicated source does not establish those releases. No native Collabora or WPS run occurred. Numerical values are independent mathematical expectations, not certification of application-specific errors, numerical tolerances or all edge cases. Formulas use English names and semicolon separators.
The help identifies the namespace COM.MICROSOFT.EXPON.DIST and says this function is outside the cited OpenFormula 1.3 standard. This format disclosure does not prove identical behavior in another product. Keep exact dotted names when checking imported workbooks.