Blend two strengths to a target strength with the alligation method: parts of each and quantities for any total.
Result
How to use this tool
Enter the higher concentration.
Enter the lower concentration.
Enter the target strength and the total quantity wanted.
Read the mixing ratio and the quantity of each ingredient.
Formula & worked example
Blending 90% and 10% solutions to 50% needs equal parts: 500 g of each for 1,000 g total.
Limitations — read this before you rely on it
Assumes linear, additive mixing of two ingredients only; it does not handle three-way blends or volume contraction on mixing.
Frequently asked questions
A classic pharmacy method for finding the proportions of two strengths that average to a target strength.
Each part count is the distance from the other strength to the target, which weights the average correctly.
Yes, for any consistent concentration units, such as mg/mL, as long as all three use the same units.
Then you need only that strength; the method requires a target strictly between the two.
Some mixtures contract or expand slightly; this method assumes additive quantities, which is fine for most pharmacy work.