Maintenance & Reliability calculator
Spare Parts Stockout Exposure Calculator
Measure observed spare-request shortages and their recorded delay burden. Enter a closed request cohort, requests not filled when needed, their mean delay and your acceptable shortage share.
What this calculator does
- Measure observed stockout frequency and recorded delays for a consistent spare-parts request cohort.
Formula used
- Stockout share = unfilled requests ÷ recorded requests × 100
- Requests filled when needed = recorded requests − unfilled requests
- Aggregate request delay = unfilled requests × mean delay
- Delay per recorded request = aggregate request delay ÷ recorded requests
- Allowance margin = maximum stockout share − observed stockout share
Inputs explained
- Recorded Spare Requests: All distinct requests in the closed stores review period.
- Requests Not Filled When Needed: Requests short of the required quantity at the required time.
- Mean Delay per Unfilled Request: Mean recorded delay across those unfilled requests.
- Maximum Unfilled Request Share: Your maximum acceptable share of requests not filled when needed.
How to use the result
- Best suited to stores service Review, spare shortage investigation.
- Observed frequency is not a forecast probability for the next request. Request delays may overlap and do not equal unique asset downtime.
Current U.S. benchmarks
- U.S. manufacturing runs at 75.7% of capacity (Federal Reserve, Aug 2026). New factory orders are up 8.5% year over year (Census).
Common questions
- Does a partial issue count as filled? Only if it meets the request’s full required quantity at the required time. Use one consistent rule across the cohort.
- Is request delay the same as machine downtime? No. Several requests may overlap, or equipment may keep running while waiting. Use unique asset event intervals to calculate downtime.
- Does this assess the consequence of a stockout? It measures request delays. Assess asset criticality, lost production and recovery costs separately when prioritizing stock.
- What if there were no requests? The stockout rate is undefined. A zero-request period provides no observed service-frequency denominator.
Last reviewed 2026-10-06.