As in the case of other methods, MTBF is calculated using an analytical method or simulation. The analytical method calculates MTBF as the reciprocal of steady state failure frequency. Steady state failure frequency is calculated in much the same way as time-specific failure frequency except steady state component availabilities are used in calculating the failure frequency.

The concept of simulation for calculating MTBF is similar to that for MTTF; however, unlike MTTF calculations, MTBF calculations consider the effects of system repairs/recoveries. The basic simulation procedure is similar to the simulation procedure used for availability calculations. Instead of counting system up and down status flags at each simulation run, the time between system failures is added to the total time between system failures. MTBF is calculated by dividing the total time between system failures by the number of simulations.