How do you calculate fan efficiency attainment?

Divide the number of fans meeting the efficiency target by the total fans efficiency tested and multiply by 100. With 44 of 50 fans passing, attainment is 88%.

What does the efficiency gap to target mean?

It is the difference between your attainment rate and your target attainment goal, in percentage points. At 88% attainment against a 92% target, the gap is 4 points short — meaning 2 more fans of the 50 needed to pass.

What is a good fan efficiency pass rate?

For a mature production line, 95%+ attainment is typical; below 90% signals a systemic issue with wheel balance, housing clearances, or drive selection. The 88% in the example would warrant a root-cause review.

Is this the same as Fan Energy Index (FEI)?

No. FEI is the efficiency ratio of a single fan versus a reference at its duty point. This metric counts how many fans in a batch met whatever efficiency target — FEI, static efficiency, or total efficiency — you set, so it tracks the line, not one unit.

Why measure attainment instead of average efficiency?

Average efficiency can hide a bimodal problem where most fans are excellent and a few fail badly. A pass-rate metric flags exactly how many units fall short of spec, which is what drives warranty and rework decisions.

How many more fans must pass to close a 4-point gap?

On a 50-fan test, each fan is worth 2 points, so closing a 4-point gap means 2 additional fans must meet target — bringing the pass count from 44 to 46.

Industrial Fans, Blowers & Air Movement Equipment calculator

Fan Efficiency Calculator

Fan Efficiency attainment measures the percentage of tested fans that met their efficiency target — useful for tracking how well a production line or a fleet of installed blowers hits its FEI (Fan Energy Index) or static-efficiency spec. Quality engineers, energy managers, and AMCA compliance teams use it to monitor whether wheels, housings, and drives are being built and trimmed to the efficiency they were designed for. It matters because under DOE fan-efficiency regulations and rising energy costs, a fan that misses target by a few static-efficiency points can cost thousands in lifetime kWh. The calculator turns pass/fail test counts into a clear attainment rate and the gap to your goal.

What this calculator does

Calculate fan efficiency attainment from fans meeting efficiency target, fans tested, and the target attainment rate.
Use it when checking whether fan designs, impeller selections, or production builds are meeting expected airflow and power performance.
It computes the percentage of efficiency-tested fans that met target, then the gap in points between that attainment rate and your target attainment goal.

Formula used

Fan efficiency attainment = fans meeting efficiency target ÷ total fans efficiency tested × 100
Fan efficiency gap to target = fan efficiency attainment - target efficiency attainment

Inputs explained

Fans meeting efficiency target:
Total fans efficiency tested:
Target efficiency attainment:

How to use the result

Use it during production efficiency audits or installed-base surveys when you have a count of fans tested and a count that passed.
It is a pass/fail count metric — it tells you how many fans met target, not by how much each one missed, so a near-miss and a gross failure count the same.

Current U.S. benchmarks

Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate fan efficiency attainment? Divide the number of fans meeting the efficiency target by the total fans efficiency tested and multiply by 100. With 44 of 50 fans passing, attainment is 88%.
What does the efficiency gap to target mean? It is the difference between your attainment rate and your target attainment goal, in percentage points. At 88% attainment against a 92% target, the gap is 4 points short — meaning 2 more fans of the 50 needed to pass.
What is a good fan efficiency pass rate? For a mature production line, 95%+ attainment is typical; below 90% signals a systemic issue with wheel balance, housing clearances, or drive selection. The 88% in the example would warrant a root-cause review.
Is this the same as Fan Energy Index (FEI)? No. FEI is the efficiency ratio of a single fan versus a reference at its duty point. This metric counts how many fans in a batch met whatever efficiency target — FEI, static efficiency, or total efficiency — you set, so it tracks the line, not one unit.
Why measure attainment instead of average efficiency? Average efficiency can hide a bimodal problem where most fans are excellent and a few fail badly. A pass-rate metric flags exactly how many units fall short of spec, which is what drives warranty and rework decisions.

Last reviewed 2026-05-12.