Alligation (Mixture) Calculator
Calculate the ratio of two solutions with different concentrations needed to achieve a desired intermediate concentration. Free online alligation calculator for pharmacy and chemistry with charts.
About This Calculator
The alligation method is a fundamental technique in pharmacy and chemistry used to determine the proportions of two solutions with different concentrations that must be mixed to obtain a solution with a desired intermediate concentration. Whether you are a pharmacist compounding medications, a chemistry student preparing lab solutions, or a medical professional formulating precise mixtures, this alligation calculator provides quick and accurate results.
The calculator uses the standard alligation formula: subtract the lower concentration from the required concentration to find the parts of the higher concentration needed, and subtract the required concentration from the higher concentration to find the parts of the lower concentration needed. The result is expressed as a simplified ratio (e.g., 1:2 or 3:4). If you provide a total volume, the calculator also determines the exact volumes of each solution required to achieve that total at the desired concentration.
How to Use
Enter the higher concentration, lower concentration, and required concentration in any consistent units (%, M, mg/mL, etc.). The required concentration must be between the higher and lower values. Optionally, enter a total volume to calculate the exact volumes of each component. Click Calculate to view the alligation ratio, simplified ratio, and volume breakdown with interactive charts.
Regional Notes
India: Alligation is a common topic in pharmacy and chemistry curricula under the Pharmacy Council of India (PCI) and is frequently tested in GPAT and NIPER exams. Pharmacists use it for compounding and extemporaneous preparations across India.
US: The alligation method is covered in US PharmD programs and is used by compounding pharmacists registered with the USP and state boards of pharmacy for preparing customized medications.
UK: Alligation is taught in pharmacy and chemistry programs accredited by the General Pharmaceutical Council (GPhC) and is used in NHS hospital pharmacy compounding and community pharmacy practice.
Frequently Asked Questions
What is the alligation method?
The alligation method is a mathematical technique used to calculate the ratio of two solutions of different concentrations that must be mixed together to produce a solution of a desired intermediate concentration. It is widely used in pharmacy, chemistry, and medicine for compounding and preparing solutions with precise concentrations.
How does the alligation calculator work?
The alligation calculator uses the alligation formula: the ratio of higher concentration to lower concentration is determined by the difference between the required concentration and the lower concentration (for higher parts), and the difference between the higher concentration and the required concentration (for lower parts). It then simplifies this ratio and optionally calculates the actual volumes needed if a total volume is provided.
Can I calculate volumes with this alligation calculator?
Yes, the calculator has an optional total volume field. When you enter the desired total volume, it automatically computes how much of the higher concentration solution and how much of the lower concentration solution you need to mix to achieve that total volume at the desired concentration.
What are common applications of alligation in pharmacy?
In pharmacy, alligation is commonly used to prepare compounded medications, mix ointments of different strengths (e.g., mixing 20% and 5% zinc oxide to get 10%), prepare alcohol solutions of specific percentages, and dilute concentrated pharmaceutical preparations to desired strengths.
Is alligation the same as dilution?
No, alligation and dilution are different. Dilution involves adding a diluent (like water) to a single concentrated solution to reduce its concentration. Alligation involves mixing two solutions of different known concentrations to achieve an intermediate concentration. Alligation uses the ratio of the two solutions, while dilution uses the formula M1V1 = M2V2.
What units can I use with this alligation calculator?
The calculator works with any concentration units (%, M, mg/mL, w/v, etc.) as long as all three concentrations use the same unit. The volume unit is in milliliters (mL), but you can use any consistent volume unit since the calculator computes ratios.
Is this alligation calculator free?
Yes, this alligation calculator is completely free to use with no registration or account required. All features including chart visualization and volume calculation are available at no cost.