Geometric Probability Calculator
Math
Calculate geometric probability with explicit inputs and a worked example.
Formula
P(X=k) = (1−p)ᵏ⁻¹p
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Independent repeated trials, counting the successful trial.
Example Calculation
Example inputs
- Success probability: 0.25
- Trial of first success: 3
For p=0.25, the first success on trial 3 has probability 0.140625.
Frequently asked questions
How do I use this calculator?
Enter success probability, trial of first success. The result updates automatically. Use Reset to restore the example values.
What method does it use?
P(X=k) = (1−p)ᵏ⁻¹p. Independent repeated trials, counting the successful trial.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.