How to calculate MTTF (Mean Time to Failure)

Hello guys,

I am studying mttf and would like a clarification. Greatly appreciate if someone could guide me.

Ok so I have a server(a) which is running/in operation 10000 hours for 1 year.

Now I have the hours at which it crashed and the number of hours it crashed. That is:

crashed at hour:|| Up again after (hours):

2350. || 3
3460. || 7
5560. || 2

Now to find the mttf i added up the hours crashed that is 12, I then did 10000-12 which gives me the up time I suppose?

Then to find mttf I did (10000-12)/3 as there are three breakdown.

Is this correct?

I used the formula mttf = total uptime/number of breakdown

Meena92 said:

Is this correct?

I used the formula mttf = total uptime/number of breakdown

Click to expand...

You do have an issue with the last 4,438 hours of operation. I assume you terminated the test at the 10,000 hour point? Note that it is possible that for that run of the equipment, the up time will have ended up exceeding 4438 hours.

If you do the calculation of (10000 - 12) / 3, you end up with a slightly conservative MTTF.

I'd likely prefer to average the actual times to failure, though it sounds like you had a good run going when you terminated at 10,000 hours