MTBF and spares
From Zenitel Wiki
How do MTBF figures relate to the percentage of items still working after a number of years. the table below provides the answer.
| Years/MTBF in thousands of hours | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 |
| 100 | 92% | 84% | 77% | 70% | 65% | 59% | 54% | 50% | 45% | 42% | 38% | 35% | 32% | 29% | 27% |
| 125 | 93% | 87% | 81% | 76% | 70% | 66% | 61% | 57% | 53% | 50% | 46% | 43% | 40% | 37% | 35% |
| 150 | 94% | 89% | 84% | 79% | 75% | 70% | 66% | 63% | 59% | 56% | 53% | 50% | 47% | 44% | 42% |
| 175 | 95% | 90% | 86% | 82% | 78% | 74% | 70% | 67% | 64% | 61% | 58% | 55% | 52% | 50% | 47% |
| 200 | 96% | 92% | 88% | 84% | 80% | 77% | 74% | 70% | 67% | 65% | 62% | 59% | 57% | 54% | 52% |
| 225 | 96% | 93% | 89% | 86% | 82% | 79% | 76% | 73% | 70% | 68% | 65% | 63% | 60% | 58% | 56% |
| 250 | 97% | 93% | 90% | 87% | 84% | 81% | 78% | 76% | 73% | 70% | 68% | 66% | 63% | 61% | 59% |
| 300 | 97% | 94% | 92% | 89% | 86% | 84% | 82% | 79% | 77% | 75% | 73% | 70% | 68% | 66% | 65% |
| 350 | 98% | 95% | 93% | 90% | 88% | 86% | 84% | 82% | 80% | 78% | 76% | 74% | 72% | 70% | 69% |
| 400 | 98% | 96% | 94% | 92% | 90% | 88% | 86% | 84% | 82% | 80% | 79% | 77% | 75% | 74% | 72% |
| 450 | 98% | 96% | 94% | 93% | 91% | 89% | 87% | 86% | 84% | 82% | 81% | 79% | 78% | 76% | 75% |
| 500 | 98% | 97% | 95% | 93% | 92% | 90% | 88% | 87% | 85% | 84% | 82% | 81% | 80% | 78% | 77% |
| 550 | 98% | 97% | 95% | 94% | 92% | 91% | 89% | 88% | 87% | 85% | 84% | 83% | 81% | 80% | 79% |
| 600 | 99% | 97% | 96% | 94% | 93% | 92% | 90% | 89% | 88% | 86% | 85% | 84% | 83% | 82% | 80% |
| 650 | 99% | 97% | 96% | 95% | 93% | 92% | 91% | 90% | 89% | 87% | 86% | 85% | 84% | 83% | 82% |
| 700 | 99% | 98% | 96% | 95% | 94% | 93% | 92% | 90% | 89% | 88% | 87% | 86% | 85% | 84% | 83% |
| 750 | 99% | 98% | 97% | 95% | 94% | 93% | 92% | 91% | 90% | 89% | 88% | 87% | 86% | 85% | 84% |
| 800 | 99% | 98% | 97% | 96% | 95% | 94% | 93% | 92% | 91% | 90% | 89% | 88% | 87% | 86% | 85% |
| 900 | 99% | 98% | 97% | 96% | 95% | 94% | 93% | 93% | 92% | 91% | 90% | 89% | 88% | 87% | 86% |
| 1000 | 99% | 98% | 97% | 97% | 96% | 95% | 94% | 93% | 92% | 92% | 91% | 90% | 89% | 88% | 88% |
| 1100 | 99% | 98% | 98% | 97% | 96% | 95% | 95% | 94% | 93% | 92% | 92% | 91% | 90% | 89% | 89% |
| 1200 | 99% | 99% | 98% | 97% | 96% | 96% | 95% | 94% | 94% | 93% | 92% | 92% | 91% | 90% | 90% |
| 1300 | 99% | 99% | 98% | 97% | 97% | 96% | 95% | 95% | 94% | 93% | 93% | 92% | 92% | 91% | 90% |
| 1400 | 99% | 99% | 98% | 98% | 97% | 96% | 96% | 95% | 95% | 94% | 93% | 93% | 92% | 92% | 91% |
| 1600 | 99% | 99% | 98% | 98% | 97% | 97% | 96% | 96% | 95% | 95% | 94% | 94% | 93% | 93% | 92% |
| 1800 | 100% | 99% | 99% | 98% | 98% | 97% | 97% | 96% | 96% | 95% | 95% | 94% | 94% | 93% | 93% |
| 2000 | 100% | 99% | 99% | 98% | 98% | 97% | 97% | 97% | 96% | 96% | 95% | 95% | 94% | 94% | 94% |