calcul dilution

What is a dilution calculation?

A dilution calculation tells you how much concentrated solution (the stock) and how much solvent you need to make a weaker solution. In labs, kitchens, aquariums, cleaning workflows, and biotech settings, this saves time and reduces mistakes. The same logic is used whether you are diluting acid, buffer, nutrient concentrate, disinfectant, or flavor extract.

If you ever asked, “How much of this strong solution do I mix with water to get the exact strength I need?”, that is exactly what calcul dilution solves.

The core equation: C1V1 = C2V2

The most common dilution formula is:

C1 × V1 = C2 × V2

• C1: concentration of stock (initial concentration)
• V1: volume of stock you must take
• C2: desired final concentration
• V2: final total volume after dilution

In most practical cases, you know C1, C2, and V2, then solve for V1:

V1 = (C2 × V2) / C1

Then compute the solvent volume:

Solvent = V2 − V1

Important unit rule

Units do not have to be specific, but they must be consistent:

• Use the same concentration unit for C1 and C2 (for example both in %, both in mg/mL, or both in mol/L).
• Use the same volume unit for V1 and V2 (for example both mL).

How to use the calculator on this page

Mode 1: Prepare target solution

• Enter stock concentration (C1).
• Enter desired concentration (C2).
• Enter final volume you want to prepare (V2).
• Click Calculate to get:
  • Required stock volume (V1)
  • Required diluent volume
  • Dilution factor and ratio guidance

Mode 2: Find final concentration

• Enter stock concentration (C1).
• Enter stock volume used (V1).
• Enter diluent added.
• Click Calculate to get final concentration (C2) and total volume.

Worked examples

Example 1: 10X buffer to 1X, final 500 mL

Given C1 = 10X, C2 = 1X, V2 = 500 mL:

V1 = (1 × 500) / 10 = 50 mL stock.

Solvent = 500 − 50 = 450 mL.

Example 2: Ethanol dilution

You have 95% ethanol and need 70% ethanol, final volume 1000 mL:

V1 = (70 × 1000) / 95 = 736.84 mL of 95% ethanol.

Add solvent to reach 1000 mL total, so about 263.16 mL solvent.

Example 3: Check final concentration after mixing

Start with 5 mg/mL stock. You take 20 mL and add 80 mL diluent.

Total volume = 100 mL. Final concentration = 5 × 20 / 100 = 1 mg/mL.

Common dilution mistakes

• Mixing unit systems: entering C1 in mg/mL and C2 in % without conversion.
• Confusing final volume with added volume: V2 is total final volume, not just solvent volume.
• Trying to “dilute up”: if C2 is greater than C1, dilution is impossible without concentrating.
• Skipping mixing step: incomplete mixing causes concentration gradients and inaccurate results.
• Rounding too early: round only at the end for better accuracy.

Practical tips for reliable results

• Use calibrated pipettes or measuring cylinders.
• Label each container immediately (name, concentration, date).
• For sensitive work, prepare slightly below final volume first, then top up to mark.
• In serial dilutions, write every step before starting to avoid chain errors.
• When handling chemicals, always follow safety guidance and wear appropriate PPE.

Quick FAQ

Can I use this for molar solutions?

Yes. As long as both concentrations use the same unit (for example M and M), the formula works directly.

What if I only know dilution ratio (like 1:10)?

A 1:10 dilution means 1 part stock in 10 total parts. So stock fraction is 1/10 of final volume; diluent is 9/10.

Is this calculator suitable for medication dosing?

Use medical tools and professional guidance for any clinical dosing. This page is a general concentration calculator, not a medical device.

Final thoughts

A good calcul dilution process is simple: pick consistent units, apply C1V1 = C2V2, and verify your numbers before mixing. With the calculator above, you can quickly get stock volume, diluent volume, dilution factor, and final concentration in just a few clicks.