Enter the number of failures, the number of units tested, and the time period into the calculator to determine the annual failure rate. This rate is expressed as a percentage and helps in assessing the reliability of a product or system over a year.

Annual Failure Rate Formula

The following formula is used to calculate the annual failure rate:

AFR = (F / (U * T)) * 100


  • AFR is the annual failure rate (%)
  • F is the number of failures
  • U is the number of units tested
  • T is the time period over which the units were tested (years)

To calculate the annual failure rate, divide the number of failures by the product of the number of units tested and the time period. Then, multiply the result by 100 to convert it to a percentage.

What is an Annual Failure Rate?

The annual failure rate is a measure of the reliability of a product or system, indicating the percentage of units that fail per year. It is a critical metric in industries such as manufacturing, electronics, and engineering, where it is essential to predict the lifespan and maintenance needs of products. A lower annual failure rate suggests a more reliable product, which is desirable for both manufacturers and consumers.

How to Calculate Annual Failure Rate?

The following steps outline how to calculate the Annual Failure Rate.

  1. First, determine the number of failures (F).
  2. Next, determine the number of units tested (U).
  3. Next, determine the time period over which the units were tested (T) in years.
  4. Next, gather the formula from above = AFR = (F / (U * T)) * 100.
  5. Finally, calculate the Annual Failure Rate (AFR) in percentage.
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Number of failures (F) = 5

Number of units tested (U) = 100

Time period (T) = 2 years