How do you calculate inventory projection accuracy?

Divide the projections within tolerance by total projections evaluated and multiply by 100. Here 8 of 250 gives 8 / 250 x 100 = 3.2%, and against a 95% target that is a 91.8-point gap.

What is a good inventory projection accuracy rate?

Strong supply planning teams project inventory within tolerance 90-95% of the time at the item level. A 3.2% result like this example signals a broken projection process, not normal variation.

Why is the gap to target reported separately?

The rate tells you where you are; the gap (91.8 points here) tells you how far from commitment you are and sizes the improvement needed, which is what a review board acts on.

What causes low projection accuracy?

Bad lead-time data, missed supply receipts, unrecorded consumption, and forecast error all corrupt projected balances. A rate as low as 3.2% usually points to a systemic data or logic error rather than scattered noise.

Projection accuracy vs forecast accuracy — what's the difference?

Forecast accuracy grades predicted demand; projection accuracy grades the predicted inventory balance, which depends on demand, supply, and current on-hand together. You can forecast demand well and still project inventory poorly if supply timing is wrong.

How do I improve inventory projection accuracy?

Clean the inputs first — lead times, open orders, and on-hand accuracy — then tighten the tolerance only after the rate climbs. Moving from 3.2% toward the 95% target closes the 91.8-point gap.

S&OP, Demand Planning & Forecasting calculator

Inventory Projection Accuracy Calculator

Inventory Projection Accuracy measures how often your projected on-hand and available-to-promise positions actually matched reality within an acceptable tolerance. Supply planners, inventory analysts, and S&OP leaders use it to judge whether the projected balances driving replenishment and allocation decisions can be trusted. It matters because every downstream decision — when to reorder, what to promise a customer, where to redeploy stock — rests on those projections; when they miss, you get surprise stockouts or bloated safety stock. The calculator turns a pile of hits and misses into a single accuracy rate and, just as importantly, the point gap to the target you committed to.

What this calculator does

Estimate inventory projection accuracy for sandop, demand planning and forecasting using production-ready inputs so teams can track KPI performance and decide whether corrective action is needed.
Use it when inventory projection accuracy in s and op, demand planning and forecasting needs a clean rate and gap-to-target you can put on a tier board.
It computes the percentage of inventory projections that fell within tolerance and the point gap between that rate and your target.

Formula used

Inventory projection accuracy rate = inventory projection accuracy count ÷ total inventory projection accuracy population × 100
Inventory projection accuracy gap to target = inventory projection accuracy rate - target inventory projection accuracy rate

Inputs explained

Inventory projections within tolerance:
Total inventory projections evaluated:
Target projection accuracy rate:

How to use the result

Use it in a monthly planning review to grade projection reliability and track it against an accuracy target over time.
A single accuracy rate hides where the misses concentrated; a portfolio can hit target overall while critical A-items project poorly, so segment before trusting the aggregate.

Current U.S. benchmarks

The producer price index for steel mill products stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. Quotes priced off last quarter's material cost miss this move.
The U.S. has 3,569 primary metal manufacturing establishments employing about 354,911 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate inventory projection accuracy? Divide the projections within tolerance by total projections evaluated and multiply by 100. Here 8 of 250 gives 8 / 250 x 100 = 3.2%, and against a 95% target that is a 91.8-point gap.
What is a good inventory projection accuracy rate? Strong supply planning teams project inventory within tolerance 90-95% of the time at the item level. A 3.2% result like this example signals a broken projection process, not normal variation.
Why is the gap to target reported separately? The rate tells you where you are; the gap (91.8 points here) tells you how far from commitment you are and sizes the improvement needed, which is what a review board acts on.
What causes low projection accuracy? Bad lead-time data, missed supply receipts, unrecorded consumption, and forecast error all corrupt projected balances. A rate as low as 3.2% usually points to a systemic data or logic error rather than scattered noise.
Projection accuracy vs forecast accuracy — what's the difference? Forecast accuracy grades predicted demand; projection accuracy grades the predicted inventory balance, which depends on demand, supply, and current on-hand together. You can forecast demand well and still project inventory poorly if supply timing is wrong.

Last reviewed 2026-05-12.