Is there any way to calculate the number of expected failures in one year based on the MTBF

The failure rate is defines as the number of failures experienced or expected for a device divided by the total equipment operating time. For constant failure rate items, i.e. exponentially distributed failures, the failure rate is the numerical inverse of the mean time between failures (MTBF). The point to remember when looking at any MTBF value is that it is an average, based on testing done on many hard disks over a smaller period of time.  MTBF = Total system operation time / Total number of failures For example; if you have 10 devices that are been testing for 8766 hours (1 year) and during the test 2 failures occur. The estimate of the MTBF is: {(10*8766) / 2} = 43830 hours/failure = MTBF 43830 devices - hours per failure is the same but with other word that 5 devices - year per failure. If you have a device that have a MTBF of the order of 200.000 hours is not say that this device should last 22 years. Must be take in account that these MTBF figures are estimates based on a theoretical model of reality, and thus are limited by the constraints of that model. There are typically assumptions made for the MTBF figure to be valid: such the terminals are operating within allowable environmental limits, and other assumptions. Example: If you know the MTBF you can know the Failure Rate, for example if the MTBF is 300.000 hours, the failure rate is F.R = 1/MTBF = 3.33 e-6 failures or 3.33 Failures per Million hour (FPMH). Also, you can know the probability that one particular terminal will be operational at time equal to MTBF (if we are working in an exponential distribution environment): R(t) = e-t/MTBF but in this case  t = MTBF  Then R (t) = e-1 = 0.368 This tell that the probability that any one particular terminal will survive to the MTBF estimated is 36.8%