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EXPONDIST Function
Summary
The EXPONDIST function calculates the exponential distribution, commonly used to model time between events in processes like service times or failure rates. It provides both probability density and cumulative distribution values for statistical analysis.
Syntax
EXPONDIST(x, lambda, cumulative)Parameters
| Parameter | Type | Required | Description |
|---|---|---|---|
| x | Number |
Yes | Value to evaluate (time or distance between events, x ≥ 0) |
| lambda | Number |
Yes | Rate parameter (events per unit time, λ > 0) |
| cumulative | Boolean |
Yes | TRUE returns CDF, FALSE returns PDF |
Using the EXPONDIST Function
EXPONDIST is perfect for modeling random arrival times, service completion times, or equipment failure intervals. Use it to calculate probabilities that a process completes within a certain time frame or the likelihood density at specific points.
Common EXPONDIST Examples
Cumulative Distribution (Process Time Analysis)
=EXPONDIST(0.2,10,TRUE)Probability that a bank teller transaction takes 0.2 minutes or less (86.47%)
Probability Density Function
=EXPONDIST(0.2,10,FALSE)Density value at 0.2 minutes with rate 10 (1.353)
Service Level Calculation
=EXPONDIST(B2,C2,TRUE)In cell D2: Probability service completes within time in B2 at rate in C2
Frequently Asked Questions
Common Errors and Solutions
#NUM! error
Cause: x < 0 or lambda ≤ 0
Solution: Ensure x ≥ 0 and lambda > 0
#VALUE! error
Cause: Non-numeric x or lambda
Solution: Use valid numbers for both parameters
Notes
- **Deprecated**: Microsoft recommends EXPON.DIST for improved accuracy
- Models memoryless processes where event probability doesn't depend on time elapsed
- PDF formula: λe^(-λx)
- CDF formula: 1-e^(-λx)
- Available in Excel 2016+ for backward compatibility
Compatibility
Available in: Excel 2016, Excel 2019, Excel 2021, Excel 2021 for Mac, Excel 2024, Excel 2024 for Mac, Excel for Microsoft 365, Excel for Microsoft 365 for Mac, Excel for the web
Not available in: Excel 2013 and earlier
Content last reviewed: December 8, 2025
Update frequency: As needed
Excel versions tested: Excel 2016, Excel 2019, Excel 2021, Excel 2021 for Mac, Excel 2024, Excel 2024 for Mac, Excel for Microsoft 365, Excel for Microsoft 365 for Mac, Excel for the web