Calculate a success rate as a percentage from successful and total attempts, or find how many successes you need to reach a target percentage.

Use whole counts from the same set of attempts.

Compare with a target percentage

Blank omits comparison. Uses the same fixed total, replacing failures with successes.

Related Calculators

Success Percentage Formula

The success percentage measures how often an attempt ends in a successful outcome. It is calculated by dividing successful attempts by total attempts and converting the result to a percentage.

SP = (SA) / (TA) × 100
Variable Meaning
SP Success percentage
SA Number of successful attempts
TA Total number of attempts

Choose the value to solve for and enter the two requested inputs. Counts must be whole numbers. The target mode rounds required successes upward; the total-attempt mode treats the entered percentage as exact and requires a matching whole-number total.

Rearranged Formulas

If you need to solve for successful attempts or total attempts instead of the percentage, use these equivalent forms:

SA = (SP) / (100) × TA
TA = (SA × 100) / (SP)

For a minimum target, round the algebraic success count upward to reach or exceed the requested percentage. The optional target comparison keeps the total fixed and asks how many failures would need to be replaced by successes; it does not add future attempts.

How to Calculate Success Percentage

  1. Count the number of successful attempts.
  2. Count the total number of attempts.
  3. Divide successful attempts by total attempts.
  4. Multiply the result by 100 to convert it into a percentage.

Total attempts must be a positive whole number, and successful attempts must be a whole number from zero through the total.

Examples

Example 1: If 75 out of 100 attempts are successful:

SP = (75) / (100) × 100 = 75%

Example 2: If 18 out of 24 attempts are successful:

SP = (18) / (24) × 100 = 75%

Example 3: If your target success percentage is 92% across 250 attempts, the number of successful attempts needed is:

SA = (92) / (100) × 250 = 230

How to Interpret the Result

  • 100% means every attempt was successful.
  • 50% means half of all attempts were successful.
  • 0% means no attempts were successful.

A higher percentage generally indicates better performance, but context still matters. A 90% success rate across 10 attempts is less informative than a 90% success rate across 10,000 attempts because the larger sample gives a more stable view of performance.

Success Percentage vs. Failure Percentage

If you also want to know the percentage of unsuccessful attempts, first calculate failures:

F = TA - SA

Then calculate the failure percentage directly or subtract the success percentage from 100:

FP = (F) / (TA) × 100
FP = 100 - SP

This is useful in quality control, customer support, sales pipelines, and sports statistics where both positive and negative outcomes are tracked.

Common Uses

  • Education: quiz accuracy, test pass rates, assignment completion success
  • Business: conversion rates, closed deals, customer retention actions
  • Manufacturing: passed inspections, accepted parts, defect-free output
  • Sports: shot accuracy, free-throw percentage, successful plays
  • Operations: completed tasks, approved applications, resolved tickets

Important Notes and Edge Cases

  • If TA = 0, the percentage cannot be calculated because division by zero is undefined.
  • If SA > TA, the inputs are inconsistent because successful attempts cannot exceed the total.
  • For a minimum target percentage, required successes are rounded upward exactly. The inverse total-attempt mode reports an error if the exact percentage and successes imply a fractional total; zero successes at 0% does not determine a unique positive total.
  • When comparing success percentages, also compare the total number of attempts so the results are not misleading.

Quick Reference Table

Task Formula
Find success percentage
SP = (SA) / (TA) × 100
Find algebraic success count (round up for a minimum target)
SA = (SP) / (100) × TA
Find total attempts (requires an exact matching whole-number total)
TA = (SA × 100) / (SP)
Find failure percentage
FP = 100 - SP

Frequently Asked Questions

Is success percentage the same as probability?
Not exactly. Success percentage usually describes observed results from actual attempts, while probability often describes the expected likelihood of success before or across repeated trials.

Can success percentage be more than 100%?
In a standard success-versus-total-attempts calculation, no. The result should normally fall between 0% and 100%.

Should I round the result?
Yes, rounding to one or two decimal places is common when the exact percentage is not a whole number.

Why does sample size matter?
A percentage based on a small number of attempts can change dramatically with one additional result, while a percentage based on a large number of attempts is usually more reliable for comparison.