Free tool

MACO & ARL Calculator

Calculate your acceptance criteria for pharmaceutical cleaning process validation.
Therapeutic dose approach (TDD) and HBEL (PDE) methods — no registration, no limits.

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Product A
Product B
Product C Optional
Shared contact surfaces per equipment train (cm²)
cm²
cm²
cm²

Results — 6 combinations

With just 3 products, there are already 6 combinations to evaluate. With 10 products, that's 90 combinations. With 50 products, 2,450. And each combination depends on the contact surface actually shared between the two products — not necessarily the same for all.

Combination (A → B) MACO (mg) ARL (mg/cm²)

Is your real case more complex?

Multiple products and multiple equipment trains? Hally-Pharma handles the complexity for you: automatic determination of shared surfaces, calculation of all your MACO and ARL for every combination — using therapeutic dose approach (TDD), HBEL and empirical (10 ppm A/B) methods.

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Frequently asked questions

The MACO (Maximum Allowable Carryover) is the maximum amount of residue from the previous product (product A) that can be tolerated in the next batch (product B) without posing a risk to patients. It is expressed in milligrams (mg) and is the fundamental acceptance criterion in pharmaceutical cleaning validation. The MACO is then converted into an ARL (acceptable residue limit per surface area) for practical application during field sampling.
The therapeutic dose approach (TDD) method applies a safety factor (typically 1/1,000) to the therapeutic daily dose of the previous product. It is the historical approach — simple but sometimes overly conservative.

The HBEL (PDE) approach uses a toxicologically derived value — the PDE (Permitted Daily Exposure) — specific to each substance. More scientifically rigorous, it is recommended by EMA and ICH Q3D guidelines. It can lead to stricter or more permissive limits depending on the actual toxicity of the molecule. For highly pharmacologically active substances, the PDE often leads to more stringent limits than the TDD method.
The ARL (Acceptable Residue Limit) is obtained by dividing the MACO by the total shared contact surface of the equipment between the two products:

ARL = MACO / S  (S in cm², MACO in mg → ARL in mg/cm²)

The ARL is the central criterion of the entire cleaning validation approach: it defines the acceptance criteria to apply during surface sampling (swabs, rinses). By comparing analytical results to the calculated ARL, one determines whether the cleaning process is qualified.