Skip to main content

Geometric Distribution Calculator

The geometric distribution models the number of Bernoulli trials required before observing the very first success.

Probability of success on any single attempt (e.g. 20% for 0.20).

The specific trial on which the first success is hypothesized to occur.

Calculated Result
12.800%

P(X = 3)

Exact P(First Success on Trial 3)

12.800%

P(Success by Trial 3)

48.800%

P(Failure through Trial 3)

51.200%

Expected Trials to First Success

5 trials

Calculation Breakdown

  1. First Success Probability FormulationP(X = 3) = (1 - p)^(k - 1) × p = (1 - 0.200)^(2) × 0.200 = 12.8000%.
  2. Cumulative Probability by Trial kP(X ≤ 3) = 1 - (1 - p)^k = 1 - 0.800^3 = 48.800%.

Probability of First Success by Trial Number (p = 20%)

Interactive visualization based on your current inputs

P(X = k)
0.05.0101520Trial 1Trial 2Trial 3Trial 4Trial 5Trial (k)Probability (%)

What Is the Geometric Distribution Calculator?

A geometric distribution calculator models waiting times until the initial occurrence of a Bernoulli event.

How Does the Geometric Distribution Calculator Work?

Multiplies cumulative failure powers by the individual single-trial success rate.

Geometric Distribution Calculator Formula & Variables

The core mathematical equation utilized by this calculator is expressed as:

P(X = k) = (1 - p)^(k - 1) × p · E(X) = 1 ÷ p

Multiplies probability of (k - 1) consecutive failures by the probability of success on trial k.

How to Use the Geometric Distribution Calculator

  1. Input your per-trial success probability percentage and your target trial number.

Step-by-Step Example Calculation

20% success rate on trial #3

Input Values:

successProbPct:20
targetTrialK:3

Understanding Your Result

Shows exact probability of first success on trial k, cumulative probability by trial k, and expected average trials.

Factors That Affect the Result

  • Per-trial probability directly dictates exponential drop-off rate.

When Should You Use This Calculator?

  • Quality control defect screening, oil well drilling success analysis, and gaming drop rate calculations.

Assumptions & Limitations

  • Trials must be independent and identical with constant probability.

Frequently Asked Questions

Calculation Accuracy & Reference Note

Standard discrete probability theory.

Explore more tools and calculators in Statistics Calculators