Reliability Calculator

Paste a failure log straight from a spreadsheet, or enter the totals, and get MTBF, MTTR, availability, and the odds of getting through a mission without a failure, per asset and overall. Then take the same metrics into Power BI as DAX.

Failure logOne failure per line: asset, failure start, repair complete (comma or tab separated, so a copy from Excel works). The asset column is optional. Dates as 2026-01-11 or 2026-01-11 14:30.In service sinceWhere each asset's first uptime period starts.

Pre-filled with the failure log from the reliability dashboard tutorial.

MTBF

288 h

Average run time between one repair and the next failure.

MTTR

9 h

Average time to get it running again once it fails.

Availability

96.97%

About 265 hours down per year.

Failure rate

3.47

Failures per 1,000 operating hours.

Mission reliability

70.7%

Chance of running 100 hours without a failure.

Expected failures

0.35

In the next 100 operating hours.

Mission lengthhoursMission figures assume a constant failure rate, which fits the flat middle of an asset's life, not break-in or wear-out.

By asset

Asset	Failures	MTBF	MTTR	Availability
AST-01	2	300 h	12 h	96.2%
AST-02	3	216 h	8.7 h	96.1%
AST-031 failure	1	480 h	4 h	99.2%

An asset with a single failure can show the best MTBF while telling you the least. Compare assets only once each has a few failures behind it.

The same metrics as DAX measures

Built on the Total Failures, Total Uptime Hours, and Total Repair Hours measures from the tutorial, with your mission length. Paste each one into New measure.

MTBF (Hours) =
DIVIDE([Total Uptime Hours], [Total Failures])

MTTR (Hours) =
DIVIDE([Total Repair Hours], [Total Failures])

Availability % =
DIVIDE([MTBF (Hours)], [MTBF (Hours)] + [MTTR (Hours)])

Failures per 1,000 Hours =
DIVIDE(1000, [MTBF (Hours)])

Mission Reliability % = -- chance of no failure in 100 hours, constant failure rate
VAR MissionHours = 100
VAR Mtbf = [MTBF (Hours)]
RETURN
    IF(NOT ISBLANK(Mtbf), EXP(-DIVIDE(MissionHours, Mtbf)))

Free, with no sign-in and no request limit. Everything runs in your browser, and nothing you paste is sent anywhere.

How uptime is counted. Each uptime period runs from the previous repair (or the in-service date, for an asset's first failure) to the next failure. Time since an asset's last repair isn't counted, so MTBF comes out conservative while an asset is still running. The reliability dashboard tutorial builds the same calculation as DAX calculated columns.

For the formulas on their own, see Reliability Metrics (MTBF, MTTR & Availability), or browse all the Power BI tools.