Introduction
When you need to make a weaker solution from a stronger one, you are performing a dilution. This dilution calculator uses the formula C1V1 = C2V2 to help you find any missing value: the stock concentration, the volume of stock needed, the final concentration, or the total volume. Just fill in three of the four fields, and the calculator solves for the fourth. It supports a wide range of concentration units (mol/L, mg/mL, ppm, % w/v, and more) along with common volume units like liters, milliliters, microliters, and gallons.
The calculator also includes a ratio-based dilution mode for when you know the mixing ratio instead of exact concentrations. For example, a 1:9 dilution means you mix 1 part solute with 9 parts solvent. Enter your ratio and total volume, and the tool tells you exactly how much of each to combine. If you provide the stock concentration, it will also calculate your final concentration after dilution. Both modes show a step-by-step breakdown of the math and a visual chart of the stock-to-solvent proportions, making it easy to double-check your work before you head to the lab or start mixing.
How to Use Our Dilution Calculator
Enter your known concentration and volume values, and this calculator will solve for the missing variable or determine how much solute and solvent you need for your dilution. It works in two modes: the C1V1 = C2V2 equation and ratio-based dilution.
C1 (Stock Concentration): Enter the concentration of your starting stock solution. Choose the unit that matches your setup, such as mol/L, mM, mg/mL, % (w/v), ppm, or ppb. This is the stronger solution you will dilute.
V1 (Volume of Stock): Enter the volume of stock solution needed, or leave this field blank to let the calculator solve for it. Pick your volume unit, such as mL, L, µL, fluid ounces, or gallons.
C2 (Desired Concentration): Enter the final concentration you want after dilution. Make sure the unit type matches C1. Use molar-based units with molar-based units and mass-based units with mass-based units.
V2 (Total Final Volume): Enter the total volume of the diluted solution you want to end up with. This includes both the stock solution and the solvent added to it. Select your preferred volume unit.
Dilution Ratio (Solute : Solvent): In the Ratio-Based Dilution tab, enter the number of parts solute and parts solvent. For example, a 1:9 ratio means 1 part solute mixed with 9 parts solvent, giving 10 total parts.
Total Final Volume (Ratio Mode): Enter the total volume of diluted solution you want to prepare. The calculator will split this volume into the correct amounts of solute and solvent based on your ratio.
Stock Concentration (Optional, Ratio Mode): If you enter your stock concentration here, the calculator will also figure out the final concentration of your diluted solution after applying the ratio.
What Is Dilution?
Dilution is the process of making a concentrated solution weaker by adding more solvent, usually water. When you dilute a solution, the amount of solute (the dissolved substance) stays the same, but the total volume increases. This means the concentration (how much solute is in a given amount of solution) goes down. Dilution is one of the most common tasks in chemistry labs, kitchens, hospitals, and many other settings.
The C1V1 = C2V2 Formula
The most important equation for dilution calculations is C1 × V1 = C2 × V2. Here is what each variable means:
- C1 is the concentration of the starting (stock) solution
- V1 is the volume of stock solution you need to use
- C2 is the concentration you want after diluting
- V2 is the total volume of the final diluted solution
This formula works because the total amount of solute before and after dilution must be equal. If you know any three of these four values, you can solve for the missing one. For example, if you have a 1 M stock solution and need 500 mL of a 0.1 M solution, the equation tells you that you need 50 mL of stock solution mixed with 450 mL of solvent.
Ratio-Based Dilution
Sometimes dilutions are described using a simple ratio instead of exact concentrations. A ratio like 1:9 means you mix 1 part of the concentrated solution with 9 parts of solvent, giving you 10 total parts. This creates a 1/10 dilution, also called a 10-fold dilution. Ratio-based dilutions are very common in biology, medicine, and cleaning product instructions. To find the volumes you need, just divide the total volume you want by the total number of parts, then multiply by each part of the ratio.
Important Things to Keep in Mind
- Units must match. When using C1V1 = C2V2, make sure your concentration units are in the same family. You cannot directly compare mol/L with mg/mL without converting first. You may need to use a molecular weight calculator to bridge between molar and mass-based units. Volume units must also be consistent or properly converted.
- C2 must be less than C1. You can only dilute a solution to a lower concentration. If you need a higher concentration than your stock, dilution will not work. You would need to add more solute or use a more concentrated stock.
- Solvent volume is V2 minus V1. The total final volume (V2) includes both the stock solution and the added solvent. So the amount of solvent you actually add equals V2 − V1, not V2 by itself.
- Dilution factor tells you how many times weaker the final solution is compared to the stock. A dilution factor of 1:10 means the final solution is 10 times less concentrated than the original.
Common Concentration Units
Concentration can be expressed in many ways depending on the field. Molarity (M) measures moles of solute per liter of solution and is the standard in most chemistry work. Milligrams per milliliter (mg/mL) and grams per liter (g/L) are common in pharmaceutical and clinical settings. Percent weight/volume (% w/v) tells you how many grams of solute are in 100 mL of solution. Parts per million (ppm) and parts per billion (ppb) are used for very dilute solutions, such as water quality testing and environmental science. One ppm equals 1 mg per liter of water. For gas-phase work, keep in mind that dilution principles apply to gaseous mixtures as well.
Everyday Examples of Dilution
Dilution is not just for science labs. When you add water to concentrated juice, you are performing a dilution. Pharmacists dilute medications to the correct dosage. Pool maintenance workers dilute chlorine to safe levels. Painters thin paint with solvents. In agriculture, fertilizer solutions are frequently diluted to the correct application rate before use. In each case, the goal is the same: reduce the concentration of a substance to the level you need while keeping the total amount of that substance under control.