Failure Rate Calculator
Calculate failure rate λ and FIT (failures per billion device-hours) from observed failures and device-hours, with the implied MTBF. Calculates in your browser.
Failure rate (FIT)
-
Show the math
The failure rate λ is failures divided by the total time observed across all devices:
λ = failures ÷ device-hours · FIT = λ × 10⁹
FIT counts failures per billion device-hours, the standard unit for component reliability. The mean time between failures is simply the reciprocal of the rate (MTBF = 1 ÷ λ). Calculated entirely in your browser.
What this does
A failure-rate calculator finds λ and FIT (failures per billion device-hours) from observed failures and device-hours.
How to use it
- Enter the number of failures.
- Enter the total device-hours.
- Read λ, FIT and the implied MTBF.
How it works
FIT is the failures expected per billion device-hours — the standard unit for component reliability. A lower failure rate means a longer MTBF.
λ = failures ÷ device-hours; MTBF = 1 ÷ λ
Understanding your result
FIT, failures per billion device-hours, is the standard unit for comparing component reliability, and it is simply the inverse of MTBF. A small absolute number here covers an enormous run time, so judge it against the population and duty cycle: two failures in a million device-hours is a very different story for two devices than for two thousand.
Example
2 failures in 1,000,000 device-hours is a λ of 0.000002, or 2,000 FIT.
Sources & methodology
Last updated .
Frequently asked questions
What is FIT?
FIT (Failures In Time) is the number of failures expected per billion device-hours. It is the standard unit for quoting component reliability.
How does it relate to MTBF?
The failure rate λ is failures divided by total device-hours, and MTBF is its reciprocal (MTBF = 1 ÷ λ). So a lower failure rate means a longer MTBF.
Is my data stored?
No. Everything is calculated locally in your browser.
Related tools
Uptime & SLA Calculator
Turn an availability target like 99.9% into the downtime it allows per day, week, month, quarter and year. See exactly what each “nine” costs. Calculates in your browser.
MTBF Calculator
Calculate Mean Time Between Failures from total operating time and the number of failures, shown in hours, days and years. Calculates in your browser.
MTTR Calculator
Calculate Mean Time To Repair from total repair time and the number of repairs, shown in hours and minutes. Calculates in your browser.
MTTF Calculator
Calculate Mean Time To Failure for non-repairable items from total operating time and the number of units, shown in hours, days and years. Calculates in your browser.