Dilution Equation Calculator (M1V1 = M2V2)
Choose which variable you want to calculate, then enter the other three values. You can mix volume units (µL, mL, L); the calculator converts automatically.
M = molarity (mol/L), V = volume
What is molarity dilution?
Molarity dilution is the process of making a less concentrated solution from a more concentrated stock solution. In chemistry and biology labs, this is one of the most common calculations you’ll perform: preparing buffers, standards, media additives, and assay reagents all depend on accurate dilution.
The core idea is that the number of moles of solute stays constant during dilution. You add solvent, not solute, so concentration changes while total moles remain the same.
The dilution formula explained
The dilution relationship is:
M1V1 = M2V2
- M1: concentration of stock solution
- V1: volume of stock solution used
- M2: desired final concentration
- V2: desired final total volume
As long as your volume units are consistent (or converted correctly), the formula works for any typical lab dilution scenario.
How to use this calculator
- Select the variable you want to find (M1, V1, M2, or V2).
- Enter the remaining three known values.
- Choose units for volume entries.
- Click Calculate to get your result instantly.
If you calculate V1, the tool also tells you how much solvent to add to reach the final volume.
Worked examples
Example 1: Prepare 100 mL of 0.50 M NaCl from a 5.0 M stock
Known values: M1 = 5.0 M, M2 = 0.50 M, V2 = 100 mL. Solve for V1:
V1 = (M2 × V2) / M1 = (0.50 × 100) / 5.0 = 10 mL
Pipette 10 mL stock, then add solvent to a final total volume of 100 mL.
Example 2: What concentration do you get?
Use 2 mL of a 1.5 M stock and dilute to 50 mL final volume.
M2 = (M1 × V1) / V2 = (1.5 × 2) / 50 = 0.06 M
Example 3: Mixed units
If V1 is entered in µL and V2 in mL, this calculator converts internally so the equation still works correctly. That helps prevent one of the most frequent dilution errors.
Common mistakes to avoid
- Confusing final volume with solvent volume to add.
- Mixing units without conversion (µL vs mL vs L).
- Using impossible targets (final concentration higher than stock in a simple dilution).
- Rounding too early during intermediate steps.
Lab best practices for accurate dilutions
- Use calibrated pipettes and appropriate tips.
- Choose volumetric glassware for critical preparations.
- Label all solutions with concentration, date, and initials.
- Document your calculation in your lab notebook for traceability.
Quick FAQ
Can I use this for serial dilutions?
Yes. Run the calculator step-by-step for each dilution stage.
Does this handle percentage concentrations?
This specific tool is for molarity (M). For % w/v or % v/v, convert to compatible concentration units first.
Can final concentration be greater than stock concentration?
Not by dilution alone. If M2 is greater than M1, you need a different stock or a concentration step (e.g., evaporation).