Dilution and Beyond-Use Date Calculator
Two compounding aids in one place. Solve any dilution using C1V1 = C2V2, then estimate a beyond-use date from USP 795 general defaults. Built for compounding pharmacists and QA teams.
Fill any three fields and leave one blank. The tool solves the blank one. Use consistent units for C1 and C2, and consistent units for V1 and V2.
Concentration of the stock you start with.
Volume of stock taken.
Concentration you want after diluting.
Total volume after diluting.
Result
Solved value
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Diluent to add (V2 minus V1)
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Add this much diluent to V1 to reach the final volume.
C1 x V1
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C2 x V2
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Date the preparation is compounded (defaults to today).
USP 795 general default for the category.
Soonest API or excipient expiry. If given, the BUD also cannot exceed 25 percent of the time left to that expiry.
Result
Beyond-use date
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Governing rule
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Category default date
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25% of remaining date
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Disclaimer: BUD defaults follow USP 795 general guidance and must be overridden by product-specific stability data and your monograph. Use the earlier of the applicable limits and document your rationale.
Dilution and BUD: FAQ
What is the C1V1 = C2V2 dilution formula?
It is the dilution equation. The amount of active substance stays the same before and after diluting, so initial concentration times initial volume (C1 x V1) equals final concentration times final volume (C2 x V2). Knowing any three values lets you solve the fourth. Use consistent units for the two concentrations, and consistent units for the two volumes.
What is a beyond-use date (BUD)?
A beyond-use date is the date after which a compounded preparation should not be used, stored, or transported. It is set from the compounding date, not the manufacturer expiry of the raw ingredients, and it accounts for the risk of chemical degradation and microbial growth once a product is opened, mixed, or repackaged.
What are the USP 795 default BUDs?
For nonsterile compounding, the general defaults are: nonaqueous formulations, not later than 6 months; water-containing oral formulations, not later than 14 days stored refrigerated; and water-containing topical, dermal, or mucosal liquid and semisolid formulations, not later than 30 days. These are maximum defaults, applied only when there is no product-specific stability information to support a longer date.
How does ingredient expiry limit the BUD?
A compounded preparation cannot outlast its ingredients. When you enter the earliest ingredient expiry, the tool also caps the BUD at 25 percent of the time remaining from the compounding date to that expiry, then reports the earlier of the category default and this cap as the final BUD.
Need compounding and stability controls that pass inspection?
We write compounding SOPs, BUD assignment procedures, and stability documentation so your preparations hold up in a PPB inspection. Talk to a regulatory pharmacist about your setup.