Exponential distribution calculator
Model waiting time between events occurring at a constant rate λ.
How do I use this page?
- Choose density, CDF, upper tail or quantile.
- Enter a positive λ.
- Enter x or probability q.
What this page does not do: The model does not fit a changing event rate or a waiting process with memory.
Further reading
Theory — what is the exponential distribution?
The exponential distribution describes the non-negative waiting time between events occurring at a constant rate λ. The parameter λ is the reciprocal of the mean waiting time, so a larger λ means shorter typical gaps between events. The calculator lets you model this waiting time and evaluate selected probabilities for a given λ. The distribution is memoryless — the remaining waiting time does not depend on how much time has already passed, unlike many other lifetime models.
Frequently asked questions
How do I choose λ?
Is density a point probability?
See also
A/B test calculator
Compare two proportions in an A/B test. Calculate conversion rates, difference, uplift, z score, p value and c
A/B test planning — sample size, MDE and duration
Plan a two-proportion experiment, estimate detectable effect and traffic duration.
ACF and PACF autocorrelation calculator
Calculate ACF and PACF across time-series lags. Review the chart, reference bounds and coefficient table.