How do you calculate screening reject rate?

Divide on-spec material passing the screen by total feed and multiply by 100 to get efficiency; the reject rate is 100 minus that. With 850 tons accepted on 1,000 tons feed, efficiency is 85%, so 15% is misplaced material.

What is a good screening efficiency?

For well-maintained aggregate screens, 90-95% is the usual target, which is why the default sets 95%. At 85% efficiency here the gap to target is 10 points, signaling blinding, worn media or overfeeding.

What is the difference between screening efficiency and reject rate?

Efficiency is the share of feed correctly sent to product; reject rate is the share misplaced. They sum to 100%. An 85% efficiency means a 15% reject or misplaced-material rate on this run.

Why is my screen efficiency dropping?

Common causes are blinded or pegged screen media, worn or holed panels passing oversize, excessive bed depth from overfeeding, and incorrect stroke or speed. Wet, sticky feed accelerates blinding and drops efficiency fast.

How does feed rate affect screening efficiency?

Overfeeding deepens the material bed so fines cannot reach the deck before discharge, cutting efficiency. Pulling feed back toward design tonnage often recovers several points without any mechanical change.

How do I close the gap to my efficiency target?

Start with the cheapest moves: clean or change blinded media, verify panel condition, and trim feed rate. Here closing the 10-point gap from 85% to the 95% target would recover 100 tons of on-spec product per 1,000 tons fed.

Bulk Solids, Mining, Aggregates & Material Processing calculator

Screening Reject Rate Calculator

Screening efficiency is the percentage of feed that a vibrating or trommel screen correctly classifies into the on-spec product stream, and its inverse is the reject or misplaced-material rate. Aggregate producers, recycling operators and mineral processors watch it because a screen that blinds, wears or runs overloaded sends saleable product to the reject pile or contaminates product with oversize. A few percent of misplaced material across a high-tonnage deck adds up to thousands of lost tons a year. This calculator converts your accepted-versus-feed tonnage into a clean efficiency figure and tells you how far you sit from target.

What this calculator does

Estimate screening reject rate for screening reject rate for bulk solids, mining, aggregates, and material processing using plant-floor material, production, quality, capacity, or cost inputs.
a plant team is reviewing screening reject rate for bulk solids, mining, aggregates, and material processing and needs a clear screening reject rate for production, quality, capacity, maintenance, purchasing, or costing decisions
It computes screening efficiency as on-spec material divided by total feed, then reports the point gap to your target.

Formula used

Screening Reject Rate = screening reject rate accepted or affected material ÷ total screen feed, oversize, undersize, fines, or saleable aggregate in same period × 100
Gap to target = target - screening reject rate

Inputs explained

On-spec material passing the screen:
Total screen feed in the same period:
Target screening efficiency:

How to use the result

Use it during screen audits, after media changes, or when product gradation drifts and you need to quantify deck performance.
A single accepted-over-feed ratio does not separate near-size carryover from true blinding; pair it with a sieve analysis to diagnose the cause behind a low number.

Common questions

How do you calculate screening reject rate? Divide on-spec material passing the screen by total feed and multiply by 100 to get efficiency; the reject rate is 100 minus that. With 850 tons accepted on 1,000 tons feed, efficiency is 85%, so 15% is misplaced material.
What is a good screening efficiency? For well-maintained aggregate screens, 90-95% is the usual target, which is why the default sets 95%. At 85% efficiency here the gap to target is 10 points, signaling blinding, worn media or overfeeding.
What is the difference between screening efficiency and reject rate? Efficiency is the share of feed correctly sent to product; reject rate is the share misplaced. They sum to 100%. An 85% efficiency means a 15% reject or misplaced-material rate on this run.
Why is my screen efficiency dropping? Common causes are blinded or pegged screen media, worn or holed panels passing oversize, excessive bed depth from overfeeding, and incorrect stroke or speed. Wet, sticky feed accelerates blinding and drops efficiency fast.
How does feed rate affect screening efficiency? Overfeeding deepens the material bed so fines cannot reach the deck before discharge, cutting efficiency. Pulling feed back toward design tonnage often recovers several points without any mechanical change.

Last reviewed 2026-05-12.