Solution Concentration Calculator (% and mol/dm³)
Calculate the percentage or molar concentration of a solution. Enter the solute mass, solution mass or molar data — instant result. Free chemistry calculator.
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Dilution Calculator (C1V1 = C2V2)
The dilution calculator lets you instantly solve any variable in the C1*V1 = C2*V2 dilution equation. Choose what to calculate: concentration after dilution (C2), final volume (V2), original concentration (C1), or volume to pipette (V1). The calculator also shows how much solvent to add. Ideal for students, chemistry teachers and lab professionals who need fast and accurate dilution calculations.
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How the dilution calculator works
The calculator is based on the conservation of solute: the number of moles (or mass) of dissolved substance does not change upon dilution. The formula C1*V1 = C2*V2 allows any of the four quantities to be calculated when the other three are known. C2 mode: C2 = (C1 * V1) / V2 — finds the concentration after dilution. V2 mode: V2 = (C1 * V1) / C2 — finds the final volume needed to reach the target concentration. C1 mode: C1 = (C2 * V2) / V1 — finds the original stock concentration. V1 mode: V1 = (C2 * V2) / C1 — finds the volume of stock to transfer. For C2 and V2 modes the calculator additionally shows the volume of solvent to add: Vadd = V2 - V1. Concentration results are clamped to 0-100%. Division by zero is handled — the result is returned as 0.
Example: preparing 0.9% saline from 10% NaCl solution
We have a 10% NaCl stock solution and need 500 mL of 0.9% physiological saline. Using V1 mode: V1 = (C2 * V2) / C1 = (0.9% * 500 mL) / 10% = 45 mL. Pipette 45 mL of the 10% stock and make up to 500 mL with water. The calculator confirms the result instantly and also shows that 455 mL of solvent must be added.
Frequently asked questions about dilution
What is solution dilution?
Dilution is the process of reducing the concentration of a solute by adding more solvent (usually water). The amount of dissolved substance remains constant while the volume increases and the concentration decreases. This is the basis of the C1*V1 = C2*V2 law.
What does C1*V1 = C2*V2 mean?
The equation C1*V1 = C2*V2 expresses the conservation of solute during dilution. C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration and V2 is the final volume. Knowing any three values you can calculate the fourth.
How do I calculate concentration after dilution (C2)?
Use the formula C2 = (C1 * V1) / V2. Example: if you have 100 mL of a 10% solution and dilute it to 200 mL, the final concentration is C2 = (10% * 100 mL) / 200 mL = 5%.
How do I calculate the final volume needed to reach a target concentration?
Use the formula V2 = (C1 * V1) / C2. Example: to obtain a 2% solution from 50 mL of a 10% stock, V2 = (10% * 50 mL) / 2% = 250 mL. You need to add 200 mL of solvent.
How much solvent do I need to add?
The volume of solvent to add equals the difference between the final and initial volumes: Vadd = V2 - V1. The calculator provides this value automatically for C2 and V2 modes. For example, if V1 = 100 mL and V2 = 300 mL, you must add 200 mL of solvent.
Does C1*V1 = C2*V2 work for different concentration units?
Yes, the formula works for any concentration units (%, mol/L, g/L) as long as C1 and C2 are in the same units and V1 and V2 are in the same volume units. This calculator uses percent (%) and millilitres (mL). Keep units consistent when using other systems.
What are the laboratory applications of the dilution law?
The dilution law C1*V1 = C2*V2 is essential for: preparing standard solutions of a known concentration, diluting concentrated acids and bases, making growth media, calibrating analytical instruments, and compounding medications and IV infusions.
Can I use this calculator for diluting strong acids?
The calculator correctly computes the C1*V1 = C2*V2 relationships for strong acids. However, always follow safety rules: when diluting strong acids, add acid to water — never add water to acid — to prevent a violent exothermic reaction. Use appropriate personal protective equipment.
How do I make a 10-fold dilution?
A 10-fold (1:10) dilution means the final volume is 10 times the initial volume: V2 = 10 * V1, so C2 = C1 / 10. Example: 1 mL sample + 9 mL water = 10 mL of a 1:10 dilution. Serial 1:10 dilutions are widely used in microbiology for colony counting.
What if the calculator shows a concentration above 100%?
The calculator automatically clamps concentration results to the 0-100% range. A concentration above 100% is physically impossible for mass-percentage solutions. If the result is clamped to 100%, the requested conditions are physically unachievable — for example, you are trying to concentrate a solution beyond its maximum possible concentration.
Results are for informational and educational purposes. The calculator assumes ideal mixing — in practice solution volumes may differ slightly from the sum of component volumes. When working with strong acids and bases, follow laboratory safety procedures.