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Circulating Load Calculator

The circulating load of a closed grinding circuit is the coarse stream recycled back to the mill, expressed relative to the fresh feed. From the fresh feed rate and the circulating (recycle) return rate this calculator returns the circulating load ratio (recycle ÷ fresh feed), the circulating load percentage, and the total mill feed (fresh feed + recycle). It is a preliminary, formula-based, educational operating mass-flow check on tonnages you supply. It is NOT a cyclone performance model, a mill-power model, or a grinding-efficiency model, and it does not calculate classification efficiency, cut size, bypass, water balance, or size distribution. Final circuit evaluation requires measured plant data, size distributions, cyclone data, mill data, and qualified review.

TypeInteractive engineering calculator

Calculator

t/h

new (make-up) feed to the closed circuit

t/h

coarse stream recycled back to the mill

Result
Circulating load ratio2.5 : 1
Circulating load250 %
Total mill feed rate350 t/h
  • !Preliminary operating mass-flow check only — this balances the fresh feed and circulating (recycle) tonnages you supply. It is NOT a cyclone performance, mill power, or grinding-efficiency model and does not calculate classification efficiency, cut size, bypass, water balance, or size distribution.

Preliminary, formula-based grinding-circuit check from user-supplied tonnages. Not equipment sizing, not vendor selection, not plant optimisation, not a circuit simulator, and not an ore-specific guarantee. Final circuit evaluation requires measured plant data, size distributions, cyclone data, mill data, and qualified review.

Related: Grinding Circuit Calculations · Screen Efficiency · Reduction Ratio · Slurry Mass Balance · Hydromet & Slurry Calculations

Formulas

Circulating load ratio
CLR = recycle / fresh feed
Circulating load percentage
CL% = CLR × 100
Total mill feed
total = fresh feed + recycle

Diagram

Circulating load — closed grinding circuit recycle balancefresh feedmillmill dischargeclassifierproductcirculating load (recycle)CLR = recycle / fresh feed CL% = CLR·100total mill feed = fresh feed + recyclean operating mass-flow check — not a cyclone or mill model

Worked example

A closed grinding circuit runs at 100 t/h fresh feed with a 250 t/h circulating (recycle) return. Find the circulating load ratio, percentage, and total mill feed.

  1. 01Circulating load ratio: CLR = 250 / 100 = 2.5
  2. 02Circulating load percentage: CL% = 2.5 × 100 = 250%
  3. 03Total mill feed: 100 + 250 = 350 t/h
Result

Circulating load ratio 2.5, circulating load 250%, total mill feed 350 t/h — a preliminary operating mass-flow check, not a cyclone or mill model.

FAQ

What is circulating load in a grinding circuit?
It is the coarse stream that a classifier returns to the mill in a closed circuit, expressed relative to the fresh feed. A circulating load ratio of 2.5 (250%) means 2.5 tonnes are recycled for every tonne of fresh feed, so the mill actually sees 3.5 times the fresh feed tonnage. It is a mass-flow ratio, not an efficiency.
Is circulating load the same as cyclone or classification efficiency?
No. Circulating load is a recycle mass-flow ratio (recycle ÷ fresh feed). Classification efficiency describes how sharply a cyclone splits coarse from fine — a partition curve with a cut size and bypass. They interact in a circuit but are different numbers; this calculator computes only the circulating load.
Why does circulating load matter?
It sets the actual tonnage passing through the mill (total mill feed = fresh feed + recycle), which affects residence time and mill throughput. Operators track it as a circuit-stability indicator, but interpreting it for sizing or optimisation needs measured size distributions, cyclone data, and mill data — outside this preliminary check.
What units should I use?
Any consistent mass-flow unit for both streams — t/h is typical. Because the ratio divides recycle by fresh feed the unit cancels, so the ratio and percentage are dimensionless; the total mill feed comes back in the same unit you entered.

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