Zerdly

Metal Recovery Calculator

This tool uses the classic two-product recovery formula: R = [c(f − t)] / [f(c − t)] × 100, where f is the feed (head) grade, c is the concentrate grade and t is the tailings grade.

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How to use this calculator

Enter Values

Enter your values and press Calculate to see results.

Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.

How to use this calculator

  1. Enter the feed (head) grade, concentrate grade and tailings grade — all three in the SAME units (all g/t for gold, or all % for base metals).
  2. Read the metal recovery %, plus the mass pull (share of feed mass reporting to concentrate) and the ratio of concentration.
  3. The two-product formula uses only the three assays — no tonnages are needed, which is why it is the standard daily metallurgical-accounting check.

How it works

This tool uses the classic two-product recovery formula: R = [c(f − t)] / [f(c − t)] × 100, where f is the feed (head) grade, c is the concentrate grade and t is the tailings grade. It is derived from a two-stream mass balance (feed = concentrate + tailings, for both mass and metal), so it returns the same recovery you would get from weighing every stream — but from grades alone. Because it is a ratio of grades, all three assays must be in identical units (all g/t, or all %).

The mass pull (fraction of feed mass reporting to concentrate) is (f − t)/(c − t), and the ratio of concentration K = (c − t)/(f − t) tells you how many tonnes of feed are needed per tonne of concentrate. The calculator guards the maths: the concentrate must be richer than the feed, the feed richer than the tailings, and c ≠ t (otherwise the denominator is zero). If any of those fail it returns a clear error rather than a nonsensical number.

Worked example

Copper flotation recovery from three assays. A copper circuit assays feed f = 1.2 %, concentrate c = 25 %, and tailings (final) t = 0.15 %. Recovery R = [25 × (1.2 − 0.15)] / [1.2 × (25 − 0.15)] × 100 = [25 × 1.05] / [1.2 × 24.85] × 100 = 26.25 / 29.82 × 100 = 88.03 %. About 12.29 % of the feed mass reports to concentrate (mass pull), a ratio of concentration of 8.14 : 1 — roughly 8.14 tonnes of feed per tonne of concentrate.

Common mistakes

  • Mixing units — entering feed and tailings in g/t but concentrate in % (or vice versa). All three grades MUST be in the same units or the ratio is meaningless.
  • Swapping concentrate and tailings. The concentrate is the rich upgraded product (highest grade); the tailings are the depleted stream (lowest grade). Reversing them gives a wildly wrong or impossible recovery.
  • Expecting exactly 100 % recovery. Real circuits lose metal to tailings, so t > 0 and recovery is always below 100 %. A computed value at or above 100 % signals a data error, not perfect metallurgy.

Frequently asked questions

What units should I use for the grades?

Any consistent grade unit works — as long as all three are the same. Use g/t (equivalent to ppm by mass) for precious metals like gold, or % for base metals like copper, zinc and lead. Because the formula is a ratio of grades, the units cancel out; only consistency matters.

Why does the formula not need tonnages?

The two-product formula is derived from balancing both total mass and metal mass across a splitting node (feed in, concentrate and tailings out). Solving those two equations lets the tonnages cancel, leaving recovery as a function of the three grades only. That is why plant metallurgists can report recovery from assays before the day's weightometer tonnes are finalised.

What is the difference between recovery and mass pull?

Recovery is the percentage of the valuable METAL that reports to concentrate. Mass pull is the percentage of the total feed MASS that reports to concentrate. A good concentrator recovers most of the metal (high recovery) into a small fraction of the mass (low mass pull) — that combination is what makes a high-grade concentrate.

How is this different from a Core Recovery or RQD calculator?

Core recovery and RQD measure how much intact drill core was physically recovered from a borehole (a geotechnical/logging measure in %). This tool measures metallurgical metal recovery — the fraction of contained metal captured in the concentrate during processing. They share the word 'recovery' but are unrelated calculations.

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