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Solution Dilution Calculator

Calculate stock volume and diluent needed to prepare a working solution using C₁V₁ = C₂V₂.

💡 Quick Summary

Calculate how much stock solution and diluent to combine when preparing a working solution at a lower concentration. Uses the dilution equation C<sub>1</sub>V<sub>1</sub> = C<sub>2</sub>V<sub>2</sub>. Supports molar, mass-based, percent, and X-fold concentration units.

📋 How to Use
  1. Enter the Stock Concentration (C1) — the concentration of your starting solution — and select its unit from the dropdown.
  2. Enter the Desired Concentration (C2) — the target concentration of your final working solution — and select its unit. Both concentrations must use compatible units (same type).
  3. Enter the Final Volume (V2) — the total volume of working solution you need to prepare — and select its unit (µL, mL, or L).
  4. Click Calculate. The result tells you exactly how much stock solution (V1) to take and how much diluent to add.
  5. Use Clear all changes to reset all fields, or Reload calculator to refresh the page.
🧮 Formulas & Logic
Dilution equation
C1V1 = C2V2
Stock volume
V1 = (C2 × V2) / C1
Diluent volume
Vdiluent = V2 − V1
📊 Result Interpretation
V<sub>1</sub> — Stock volume

The volume of concentrated stock solution you need to pipette. Add this to the diluent to reach the target concentration.

V<sub>diluent</sub>

The volume of solvent (water, buffer, etc.) to add to V1. Together, V1 + Vdiluent = V2.

Unit compatibility

C1 and C2 must be in the same concentration category (e.g. both molar, both mass-based, both percent). Mixing categories (e.g. mM and mg/mL) is not valid.

X-fold dilution

When using X-fold units (e.g. 10× stock), C1 = 10 and C2 = 1 gives the volumes needed to make a 1× working solution.

🔬 Applications
  • Preparing working solutions from concentrated reagent stocks in molecular biology
  • Diluting cell culture media, buffers, and enzyme solutions
  • Making standard curves for ELISA, colorimetric assays, and spectrophotometry
  • Diluting antibody stocks for western blot, IHC, or flow cytometry
  • Pharmaceutical compounding and dilution of IV drug solutions
  • Preparing serial dilutions for minimum inhibitory concentration (MIC) assays
  • Diluting fluorescent dyes and stains for microscopy
⚠️ Common Mistakes & Warnings
C2 must be less than C1

This calculator performs dilution, which always decreases concentration. If your desired concentration equals or exceeds the stock concentration, you cannot dilute to reach it.

Mix into the diluent, not the other way around

When working with concentrated acids, bases, or hygroscopic salts, always add the stock solution to the diluent (never add water to acid). The calculator gives the correct volumes but does not account for mixing order safety.

Make up to final volume in a volumetric flask

For accurate molarity, add the stock to the diluent and then make the mixture up to V2 in a volumetric flask. Do not simply add Vdiluent to V1 unless volumetric accuracy is not critical.

❓ Frequently Asked Questions

What is the C1V1 = C2V2 formula?
The dilution equation states that the amount of solute (concentration × volume) is conserved when you dilute a solution. C1 and V1 are the concentration and volume of the stock solution; C2 and V2 are the target concentration and final volume. Rearranging gives V1 = (C2 × V2) / C1.
Can I mix different unit types, e.g. mM for C1 and µM for C2?
Yes — both are molar units so they are compatible. The calculator automatically converts them to a common base before computing. What you cannot mix is a molar unit with a mass-based unit (e.g. mM and mg/mL), because those represent fundamentally different quantities.
How do I use X-fold units?
Enter the fold-concentration of your stock as C1 (e.g. 10 for a 10× stock) and the desired working fold as C2 (e.g. 1 for a 1× working solution), then enter the final volume V2. Both must use the X unit.
What is the diluent?
The diluent is the solvent you add to the stock — typically distilled water, PBS, culture medium, or another appropriate buffer. The calculator tells you how much to add (V2 − V1), but the choice of diluent depends on your experiment.
What if I need a very small V1 (less than 1 µL)?
When V1 is too small to pipette accurately, perform a serial dilution: make an intermediate dilution first to bring the concentration closer to C2, then do a second dilution from the intermediate. Most pipettes cannot reliably dispense less than 0.5 µL.

Dilution equation: C₁V₁ = C₂V₂ — the amount of solute is conserved during dilution.