Why is 3% across 10 attempts not exactly 30%?
Because each attempt can miss. The formula calculates the chance of missing every attempt first, then subtracts that from 100%.
Repeated Attempt Probability Calculator
A browser-based calculator for estimating the chance of at least one success across repeated independent attempts.
What Repeated Attempt Probability Calculator is used for
The Repeated Attempt Probability Calculator estimates the chance of at least one success after several independent attempts with the same success rate.
- Best for
- Understanding repeated attempts when each try has the same success rate
- Cost
- Free to use
- Login
- No account required for normal calculator use
- Use case
- Calculating the chance of at least one success after multiple attempts
What this tool is
The Repeated Attempt Probability Calculator estimates the chance of at least one success after several independent attempts with the same success rate.
Tool overview
This model is useful for simple probability education because it shows both the success chance and the miss chance. It is often safer than only looking at the advertised single-attempt rate.
Who it is for
- Students learning probability basics
- People comparing risk across repeated attempts
- Collectors checking random draw risk before making a decision
Problems it helps solve
- Calculating the chance of at least one success after multiple attempts
- Understanding the miss chance that remains after repeated tries
- Avoiding the mistake of multiplying the single-attempt rate by the number of attempts
Main features
- At least one success probability
- Miss chance calculation
- Single-attempt rate input
- Repeated attempt model
- Plain-English risk explanation
How to use it
- Enter the single-attempt success rate as a percentage.
- Enter the number of independent attempts.
- Compare the at-least-one success chance with the chance of missing every attempt.
- Use the result as an educational estimate, not a prediction.
Example use case
Checking repeated random attempts
If a target has a 3% chance on one attempt and you try 10 times, the chance of at least one success is about 26.26%, not 30%. The miss chance is still about 73.74%.
- Set the single-attempt success rate to 3.
- Set attempts to 10.
- Read both the success chance and miss chance.
- Use the result to understand risk before making a time, budget, or planning decision.
Limitations
- The model assumes each attempt is independent and has the same success rate.
- It does not handle pity systems, changing rates, shrinking pools, or hidden rules.
- It cannot predict a specific result or guarantee success.
Privacy note
The calculator runs in the browser and does not require account registration. Inputs such as rate and attempt count are normal calculator values.
FAQ
What does independent attempt mean?
It means one attempt does not change the success rate of the next attempt. If the rate changes after each attempt, this calculator is not the right model.
Can this calculator guarantee a result?
No. It explains probability under a simple model. Random outcomes can still miss even when the success percentage looks high.
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