How do you calculate inspection defect rate for glass containers?

Divide rejected containers by inspected containers and multiply by 100. With 420 rejects out of 52,000 inspected, that is 420 ÷ 52,000 × 100 = 0.81%.

What is a good defect inspection rate for a bottle line?

Strong container glass cold-end reject rates often sit below 1%, with premium cosmetic ware tighter still. The 0.81% in our example is inside a 0.7% target only by a small margin — the gap of -0.11 points means it is actually above target and worth investigating.

What does a negative defect-rate gap to target mean?

The gap is your actual rate minus the target. A negative number means your measured rate is below target, which is good; here the gap shows -0.11 points but because the formula subtracts target from actual, the example actually sits 0.11 points over the 0.7% goal.

Why is my inspection defect rate spiking on one cavity?

A single-cavity spike almost always points to a forming-section issue — worn mold, blocked vent, baffle or plunger wear, or a gob loading problem — rather than a plant-wide cause. Drill into per-cavity reject codes before adjusting the whole machine.

Is inspection defect rate the same as pack rate loss?

No. Inspection defect rate is rejects at the cold-end inspection machines; pack-to-melt and pack rate also include hot-end checks, breakage, and sampling losses. Defect inspection rate is one input into overall pack efficiency, not the whole picture.

How many containers should I inspect before trusting the rate?

With reject rates near 1%, you want tens of thousands of containers for a stable number — a 52,000-container shift gives roughly 420 rejects, enough to trend reliably; a few hundred containers will swing wildly.

Glass Container & Bottle Manufacturing calculator

Defect inspection rate Calculator

Inspection defect rate is the share of glass containers pulled at the cold-end inspection station — for split bottoms, checks, blisters, and dimensional faults — divided by everything the inspection equipment screened. Quality engineers and cold-end supervisors in container glass plants watch it shift by shift because it is the fastest read on whether the IS machine, gob delivery, or annealing lehr is drifting. A rate climbing past the target reject line usually means a forming section needs attention before pack rate suffers downstream. It is reported per line, per mold cavity, and per defect family so the plant can chase the real root cause.

What this calculator does

Calculate inspection defect rate for glass bottles, jars, and containers using rejected containers, inspected containers, and the target defect rate.
Use it when quality teams need to track checks, stones, blisters, seeds, cracks, birdswings, finish defects, dimensional rejects, labeling damage, or vision-system rejects against the control target.
It computes the percentage of inspected glass containers rejected at cold-end inspection and the gap between that rate and your reject target.

Formula used

Defect inspection rate = rejected containers at inspection ÷ inspected containers × 100
Defect inspection rate gap to target = defect inspection rate - target defect rate

Inputs explained

Rejected containers at inspection:
Inspected containers:
Target defect rate:

How to use the result

Use it every shift on each forming line, and after any mold change, gob weight adjustment, or lehr setpoint change to confirm the defect rate settled back inside target.
It only counts defects the inspection machines actually detect — undetected hairline checks or faults below the camera threshold pass through, so this rate understates true quality escapes.

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 inspection defect rate for glass containers? Divide rejected containers by inspected containers and multiply by 100. With 420 rejects out of 52,000 inspected, that is 420 ÷ 52,000 × 100 = 0.81%.
What is a good defect inspection rate for a bottle line? Strong container glass cold-end reject rates often sit below 1%, with premium cosmetic ware tighter still. The 0.81% in our example is inside a 0.7% target only by a small margin — the gap of -0.11 points means it is actually above target and worth investigating.
What does a negative defect-rate gap to target mean? The gap is your actual rate minus the target. A negative number means your measured rate is below target, which is good; here the gap shows -0.11 points but because the formula subtracts target from actual, the example actually sits 0.11 points over the 0.7% goal.
Why is my inspection defect rate spiking on one cavity? A single-cavity spike almost always points to a forming-section issue — worn mold, blocked vent, baffle or plunger wear, or a gob loading problem — rather than a plant-wide cause. Drill into per-cavity reject codes before adjusting the whole machine.
Is inspection defect rate the same as pack rate loss? No. Inspection defect rate is rejects at the cold-end inspection machines; pack-to-melt and pack rate also include hot-end checks, breakage, and sampling losses. Defect inspection rate is one input into overall pack efficiency, not the whole picture.

Last reviewed 2026-05-12.