In formulation work, the label claim fixes the API dose and development fixes the percentage that API should make up in the tablet. The theoretical tablet weight follows from those two numbers. This is the figure that compression, in-process control and weight variation limits are all built on.
Once the tablet weight is known, each excipient percentage is converted to milligrams per tablet. The balance check tells you whether the API and the excipients together reach 100%, which catches a formulation entry error before it reaches the batch record.
A tablet contains 500 mg of API, which is 62.5% w/w of the formula.
Tablet weight = 500 ÷ 0.625 = 800 mg.
| Component | % | mg per tablet |
|---|---|---|
| API | 62.5 | 500.0 |
| Microcrystalline cellulose | 20.0 | 160.0 |
| Binder | 8.0 | 64.0 |
| Disintegrant | 5.0 | 40.0 |
| Glidant | 3.0 | 24.0 |
| Lubricant | 1.5 | 12.0 |
| Total | 100.0 | 800.0 |
The balance is exact, so the formula is complete.
Keep the percentage column and the milligram column side by side in the master formula, and recheck both whenever the API potency, the salt form or the label claim changes. A change in any one of them moves the tablet weight, the die and punch selection, and the weight variation limit that applies to the product.
For a new formulation, compare the calculated weight with the tablet size the press tooling can handle. A very heavy tablet may need a different shape or a granulation step to keep it swallowable. For an existing product, use the calculated weight as the reference when setting the in-process target and its control limits on the compression line.
Document the source of every percentage. During an inspection or an investigation, the first question is usually which approved version of the formula the batch was manufactured against.
The calculated tablet weight is copied into the master formula next to the percentage of each component, and it becomes the target for compression. Record the version of the formula used for the calculation, because a later change in potency or in an excipient percentage changes the weight. Check the final figure against the die fill capacity of the tooling before the first batch.
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.
Because the dose is fixed by the label claim and the percentage is a formulation decision. The tablet weight is the result, not the starting point.
No. It calculates the core tablet. Use the Coating Material Calculator for the film coat.
Recheck each percentage and the API percentage. A shortfall means a missing component, and an excess means a double-counted or mistyped one.
Related tools and guides: Weight Variation Calculator · Coating Material Calculator · Batch Size Calculator
By Sajjad Ahmad. For reference and education only; verify limits against your SOPs and the current pharmacopoeia. See the methodology.