Solution Blending / Concentration Mixing Calculator
Blend two solutions to find the resulting concentration, or work backwards to find exactly how much of each stock solution you need to hit a target concentration and final volume or mass — by molarity or mass percent.
Choose how to measure your solutions, then enter the known values.
Blended molarity
Formula used: C(final) = (C₁V₁ + C₂V₂) / (V₁ + V₂)
0.46 M
Final molarity
0.5 mL
Total volume
0.2 mL
Solution A volume
0.3 mL
Solution B volume
Interactive Blending Visual
Two source containers combining into one final blended solution, with concentration bars scaled to strength.
Step-by-Step Solution Blending Calculation
Here's exactly how this answer was calculated, one step at a time.
Given: C₁ = 1 M, Volume A = 200 mL, C₂ = 0.1 M, Volume B = 300 mL
Step 1: Use the weighted-average blending formula
The final molarity of a blend is a weighted average of each solution's molarity, weighted by how much of each you use.
C(final) = (C₁V₁ + C₂V₂) / (V₁ + V₂)Step 2: Insert the known values
C₁ = 1 (base units); Volume A = 0.2; C₂ = 0.1; Volume B = 0.3Step 3: Multiply each concentration by its quantity, then add
(1 × 0.2) + (0.1 × 0.3) = 0.23Step 4: Divide by the total combined quantity
0.23 ÷ 0.5 = 0.46
Calculated result:
0.46 M
Solution Blending & Concentration Mixing Calculator: Free Online Tool
This solution blending calculator answers two everyday chemistry questions: what concentration do I get when I mix two solutions together, and how much of each solution do I need to hit a specific target concentration. It works with molarity and volume, or with mass percent and mass, so it fits both a chemistry lab bench and an industrial or food-production mixing tank.
Under the hood it uses the same alligation method pharmacists, lab technicians, and process engineers have relied on for generations: a weighted average based on how much of each solution goes into the mix. Enter your two stock concentrations and either the amounts you plan to use, or the target you want to reach, and the calculator handles the algebra, the unit conversion, and the full step-by-step working.
Why You Need a Concentration Mixing Calculator
Blending solutions comes up constantly: diluting a stock reagent with a weaker one instead of pure solvent, combining two batches of syrup or brine to hit a house-standard concentration, or mixing a strong acid with a weak acid to reach a process specification. Doing this by hand means solving two equations at once, and a small arithmetic slip can waste an entire batch.
A dedicated blending calculator removes that risk. It keeps units straight, shows every step of the working so you can double-check the logic, and instantly flags an impossible target — for example, asking for a concentration higher than both of your starting solutions, which is physically impossible without adding more of the stronger one.
The Solution Blending Formula: Weighted Average
When you combine Solution A (concentration C1, quantity V1) with Solution B (concentration C2, quantity V2), the resulting concentration is a weighted average: C(final) = (C1×V1 + C2×V2) / (V1 + V2). Each solution's contribution to the mix is weighted by how much of it you actually add, not just its concentration alone.
For example, mixing 200 mL of a 1.0 M solution with 300 mL of a 0.1 M solution gives (1.0×200 + 0.1×300) / (200+300) = (200+30)/500 = 0.46 M. Notice the result sits closer to the weaker solution's concentration because there is more of it in the final mix — a larger volume pulls the average toward itself.
Working Backwards: Hitting a Target Concentration (Alligation)
The more useful question is often the reverse one: I have two stock solutions and I need a specific final concentration and final volume — how much of each do I use? This is the classic alligation problem, and it is solved by combining two equations: V1 + V2 = V(final), and C1×V1 + C2×V2 = C(target) × V(final).
Solving that system gives a clean formula for the first solution: V1 = V(final) × (C(target) − C2) / (C1 − C2). Once V1 is known, V2 follows immediately as V(final) − V1. This calculator's target mode runs exactly this method and also checks that your target concentration actually sits between C1 and C2, since a blend can never be stronger than your strongest stock or weaker than your weakest one.
Blending by Volume and Molarity
For aqueous chemistry solutions — buffers, acids, bases, salt solutions, reagents — blending by volume and molarity is the standard approach. Enter each solution's molarity in M, mM, or µM, and its volume in litres, millilitres, microlitres, or US gallons. The calculator converts everything to a common base internally before running the blend so your inputs never need to share the same unit.
This mode is ideal for laboratory dilution and reagent preparation, buffer blending in biochemistry, and any process where volumes are measured with pipettes, burettes, or graduated cylinders.
Blending by Mass and Mass Percent
For syrups, brines, industrial cleaning solutions, and concentrated acids or bases, mass percent (% w/w) is usually the more accurate way to blend, because mass adds perfectly even when volumes do not. Switch the calculator's blend basis to 'Mass & Mass Percent' to enter each solution's strength as a percentage and its quantity as a mass in grams, kilograms, milligrams, pounds, or ounces.
The same weighted-average formula applies, just swapping volume for mass: C(final) = (C1×m1 + C2×m2) / (m1 + m2). Mass-based blending is the safer choice whenever the two liquids being mixed have noticeably different densities, since combining volumes of liquids with different densities does not give an exactly additive final volume.
Why Volumes Are Not Always Perfectly Additive
A subtle but important chemistry fact: when you mix two liquids, especially concentrated ones, the final volume is not always exactly equal to the sum of the two starting volumes. Strong sulfuric acid mixed with water, for example, contracts slightly because water molecules pack more tightly around dissolved ions. This effect is called volume contraction.
For dilute aqueous solutions — most buffers, dilute acids, and typical lab reagents below a few molar — this contraction is small enough to ignore for everyday calculations. For concentrated acids, bases, alcohols, or industrial process liquids, mass-based blending avoids the issue entirely, since mass is always perfectly additive regardless of any volume change during mixing.
Worked Example: Diluting With a Weaker Stock Instead of Pure Solvent
Suppose a lab has 1.0 M hydrochloric acid and a leftover batch of 0.1 M hydrochloric acid, and needs 500 mL of 0.4 M solution instead of throwing the weaker batch away. Using the target mode: V1 = 500 × (0.4 − 0.1) / (1.0 − 0.1) = 500 × 0.3/0.9 ≈ 166.7 mL of the 1.0 M stock, and V2 = 500 − 166.7 ≈ 333.3 mL of the 0.1 M stock.
This is a common real-world move — using a weaker existing solution as the diluent instead of buying or preparing fresh solvent — and it saves both material and money once you know the exact ratio the alligation method gives you.
Solution Blending in Industry and the Lab
Pharmacists use alligation daily to compound a specific-strength cream, solution, or syrup from two stock strengths on the shelf. Beverage and food manufacturers blend concentrate batches with water or weaker batches to standardise a final product's Brix, salinity, or acidity. Water treatment plants blend chemical dosing solutions to hit a precise target concentration before injection.
In the lab, blending two existing reagent stocks instead of diluting from a pure solvent is a fast, low-waste way to prepare an intermediate concentration for a calibration curve, buffer series, or titration standard. Understanding the underlying weighted-average math means you are never stuck if a fresh stock solution is not available.
Common Mistakes When Blending Solutions
The most frequent mistake is treating a blending problem as a simple average of the two concentrations, ignoring the quantities. Mixing equal parts of 1.0 M and 0.1 M gives 0.55 M, but mixing unequal parts changes that result significantly — the formula must always weight by quantity, not just count the two concentrations.
A second mistake is requesting a target concentration outside the range of your two stock solutions. No combination of a 1.0 M and a 0.1 M solution can ever produce a 1.2 M or a 0.05 M result — the target must fall between the two starting concentrations. This calculator checks for that automatically and flags an impossible target instead of returning a misleading negative or oversized volume.
Tips for Accurate Solution Blending
Always confirm your stock concentrations are current and correctly labelled before blending — an old, evaporated, or mislabelled stock throws off every downstream calculation. Measure with equipment appropriate to your precision needs: volumetric pipettes and flasks for lab work, calibrated tanks or flow meters for industrial batches.
When mixing concentrated acids or bases, always add acid to water rather than water to acid, and follow proper safety procedures regardless of what the calculator's numbers say — chemical safety takes priority over calculation convenience every time.
Solution Blending Calculator FAQ and Quick Reference
To find a blend's resulting concentration, use C(final) = (C1V1 + C2V2)/(V1+V2). To find how much of each stock you need for a target, use V1 = V(final) × (C(target) − C2)/(C1 − C2), then V2 = V(final) − V1. A target concentration must always sit between your two stock concentrations, and mass-based blending is more reliable than volume-based blending for concentrated or non-aqueous liquids.
This free online solution blending and concentration mixing calculator is intended for educational and laboratory-planning use. For regulated, clinical, pharmaceutical, or safety-critical work, always verify results independently and follow your organisation's validated procedure.
Frequently Asked Questions
What is the formula for blending two solutions?
The final concentration is a weighted average: C(final) = (C1×V1 + C2×V2) / (V1+V2), where V1 and V2 are the quantities of each solution used.
How do I find how much of each solution to mix for a target concentration?
Use the alligation formula V1 = V(final) × (C(target) − C2) / (C1 − C2), then find V2 by subtracting V1 from the target total quantity.
Can I blend two solutions to get a concentration higher than both?
No. A blend's concentration must always fall between the concentrations of the two solutions used to make it.
Should I blend by volume or by mass?
Volume and molarity work well for dilute aqueous solutions; mass and mass percent are more accurate for concentrated acids, bases, or liquids with different densities, since mass is always perfectly additive.
Why are volumes sometimes not exactly additive when mixing liquids?
Some liquids, especially concentrated acids mixed with water, undergo slight volume contraction on mixing, so the final volume can be marginally less than the sum of the two starting volumes.