How the Compression Reconciliation Calculator works

Compression reconciliation converts the weight of the granules fed to the press and the weight of tablets produced into tablet counts, then compares them. Counting by tablets rather than by weight keeps the reconciliation consistent with the later stages, where the batch is tracked in units.

The calculator gives the theoretical tablet count, the actual tablet count and the percentage yield.

Compression arithmetic

Example: 100.0 kg of granules, 400 mg tablets

100.0 kg of lubricated granules go to the press. The core tablet weight is 400 mg. The compressed tablets weigh 96.8 kg.

1. Theoretical tablets = 100.0 × 1,000,000 ÷ 400 = 250,000
2. Actual tablets = 96.8 × 1,000,000 ÷ 400 = 242,000
3. % Yield = 242,000 ÷ 250,000 × 100 = 96.8%

The 8,000 tablets difference is made up of rejects, samples, powder and tablets lost at start-up and shut-down, and any unexplained loss.

Compression yield limits

• Limits: yields in the high 90s are typical for a well-controlled compression run, but the acceptance limit comes from the master batch record.
• Weights in kilograms: the factor 1,000,000 converts kilograms to milligrams. Entering grams will give a count a thousand times too small.
• Tablet weight: use the approved target core weight. If the actual average weight differs, the count based on weight will differ too.
• Accounting: rejects, samples, sweepings and returned powder should each be weighed and recorded.

Practical tips for compression stage checks

A low yield with normal weights usually points to material loss at the press, such as dust extraction, spillage, rejects from metal detection or de-dusting, and tablets discarded at start-up. A low yield together with high weight variation points to a feeding or die-fill problem. Compare the result with the weight variation records for the same run before deciding on the cause.

Compression reconciliation errors

• Entering the weight in the wrong unit, so the tablet count is out by a factor of 1,000.
• Using the coated tablet weight instead of the core weight.
• Ignoring sweepings and rejects in the actual quantity.
• Using the nominal weight when the average actual weight has shifted.
• Not reconciling the lubricated blend weight against the weight actually fed to the press.

If compression yield is outside the limit

First confirm the arithmetic: the granule weight fed to the press, the units used for the tablet weight and the factor of 1,000,000. Then account for the physical losses in a fixed order. Weigh the rejected tablets, the samples taken for in-process checks and the powder and tablets removed at start-up and shut-down. Add the contents of the dust extraction and the de-duster. If a gap remains after these are included, review the press log for stoppages and check whether tablets were removed for any other purpose. The gap that is left is treated as a deviation and investigated with the batch record.

Standards and references

The checks on this page relate to the documents below. Standards are revised from time to time, so confirm the current edition and follow your own approved procedures.

• 21 CFR 211.103, Calculation of yield
• 21 CFR 211.188, Batch production and control records
• 21 CFR 211.192, Production record review
• EU GMP Part I, Chapter 5, Production

Related tool: the Tablet Friability Calculator checks how well tablets resist abrasion and breakage.

Questions on compression reconciliation

How do I convert tablet weight into a number of tablets?

Convert the total weight to milligrams and divide by the core tablet weight in milligrams.

What is a normal compression yield?

High 90s are typical for a well-controlled run, though the acceptable threshold depends on the product and your SOP.

Why count tablets instead of comparing weights?

The count carries forward unchanged to coating and packing, where the weight per unit differs.

Related tools and guides: Batches per Month · Cost of a 1% Yield Drop · Force to Pressure Guide · Setting Yield Limits · Weight Variation Test Guide · Batch Reconciliation Explained · Percentage Yield Calculator · Weight Variation Calculator · Coating Reconciliation

By Sajjad Ahmad. For reference and education only; verify limits against your SOPs and the current pharmacopoeia. See the methodology.