Alligation (mixing two strengths)
Parts and amounts of a higher and a lower strength to make a desired strength.
Inputs
1 of 4%
0 for a plain base or diluent.
%
%
g or mL
When to use
- Compounding a strength between two stock strengths.
Pearls and pitfalls
- Use 0% for a diluent or base.
- Works for percentages, ratio strengths converted to percent, or concentrations in the same unit.
Why use
The classic pharmacy method, with the grid shown.
Parts of higher = desired − lower; parts of lower = higher − desired; amount = total × parts ÷ (sum of parts)