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Compounding calculator

Free

Enter your base formula and batch sizes. The calculator scales each ingredient quantity proportionally and produces a printable compounding worksheet. Add up to 15 ingredients per formula.

Ingredient name
Qty (base)
Unit
Compounding worksheet
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Pharmaceutical compounding: scaling formulas accurately

Compounding is the preparation of a customised medication for an individual patient when a commercially available product doesn't meet their needs. Accurate formula scaling is critical, errors in ingredient quantities can lead to subtherapeutic, toxic or contaminated preparations. In the US, pharmacy compounding for an identified patient operates under Section 503A of the Federal Food, Drug and Cosmetic Act, which exempts it from standard FDA drug-approval requirements provided the conditions of that section are met.

Proportional scaling

Every ingredient quantity scales by the same factor: new quantity = original quantity × (target batch / base batch). For a 100g base formula scaled to 250g, every ingredient is multiplied by 2.5. This calculator handles the arithmetic for up to 15 ingredients simultaneously, reducing transcription errors. When ingredients are sourced in different units than your formula calls for, our Pharmacy Unit Converter handles the conversion before you scale.

Beyond-use dating (USP guidelines)

USP Chapter 795 (non-sterile) guidelines: non-aqueous preparations (creams, ointments, suppositories), up to 6 months BUD. Water-containing oral formulations, 14 days refrigerated. Topical/dermal aqueous preparations, 30 days. Sterile preparations follow USP 797 with much stricter requirements. Always verify current USP guidelines, which are updated periodically.

Documentation requirements

A compounding master formula record must include: preparation name and strength, ingredients and quantities, equipment, procedures, quality checks, BUD and storage. This calculator generates a worksheet that can form the basis of your compounding record, verify against your facility's requirements before use. Pair this with our Concentration Calculator for solution strength verification.

Frequently asked questions

Multiply each ingredient quantity by the ratio of the new batch size to the original batch size. If the original formula makes 100g and you need 250g, multiply each ingredient by 2.5. This calculator automates that process for up to 15 ingredients simultaneously.
Beyond-use date (BUD) is the date after which a compounded preparation should not be used. Unlike manufactured drugs, compounded preparations don't have expiry dates based on stability studies. In the absence of stability data, USP guidelines set default non-sterile BUDs of up to 6 months for non-aqueous formulations, 14 days refrigerated for water-containing oral formulations, and 30 days for water-containing topical, dermal and mucosal formulations.
A master formula record specifies every ingredient and its quantity per batch, the manufacturing procedure, equipment, quality checks, BUD and storage conditions. Regulatory bodies require a master formula record for each compounded preparation as part of quality assurance documentation.