Dilute to Exact Final Volume Calculator

Top up an existing sample to a measured final volume, or choose fixed-volume stock dilution to calculate an aliquot for a specific target concentration.

Reach an exact volume

Top up an existing sample without a concentration calculation, or use the fixed-volume stock dilution workflow.

Try an example
Workflow

Concentration basis: Use molarity (M, mM, µM, nM, pM) or % v/v throughout a calculation. % v/v is the volume of a liquid component per 100 volume units of final solution; it is not % w/v or % w/w. These tools do not convert between concentration categories or percentage bases. Solute must be conserved. Calculated added volumes and mixture concentrations assume additive solution volumes; measure the final volume for precise preparation.

Prepare a solution to a measured final volume

Use fixed-volume stock dilution when you need a defined concentration in a defined final volume. The stock aliquot is calculated from the same solute balance as C₁V₁ = C₂V₂:

V₁ = C₂V₂/C₁

Here C₁ is the stock concentration, C₂ is the target concentration, V₁ is the stock aliquot, and V₂ is the exact final volume. The stock must be at least as concentrated as the target, with compatible molarity units or the same % v/v basis. For % v/v, the balance conserves the equivalent liquid-component volume rather than moles.

For example, to make 100 mL of 50 mM solution from 1 M stock, V₁ = 0.050 × 100 / 1 = 5 mL. Transfer 5 mL of stock and bring to 100 mL total. The estimated diluent volume is 95 mL; adding 100 mL of diluent would overshoot.

Using a volumetric flask

  1. Choose a clean volumetric flask with the required final volume and a suitable pipette for the stock aliquot.
  2. Transfer the measured aliquot and add compatible diluent according to the chemical’s handling procedure. Mix while still below the calibration mark.
  3. Let the solution equilibrate to the flask’s calibration temperature before making the final adjustment, especially if mixing changes its temperature.
  4. Add diluent dropwise near the mark. For a clear solution with a concave meniscus, align its bottom with the mark at eye level to avoid parallax.
  5. Stopper and invert repeatedly to distribute the solution uniformly, including the liquid in the neck.

See the University of Wisconsin volumetric-flask guidance for filling and meniscus reading. For mixtures that generate substantial heat, follow the laboratory procedure for initial mixing and cooling before volumetric adjustment.

Top up an existing sample

If concentration is not part of the calculation, use the default top-up mode. Starting with 500 µL and bringing to 2 mL requires an estimated 1.5 mL of diluent. This mode reports volume only; it cannot determine final concentration without knowing the original solute amount.

Calculated diluent volume versus measured final volume

The displayed diluent estimate is V₂ − V₁ and assumes additive volumes. Real mixtures may contract or expand, so a precise preparation uses the final calibration mark rather than relying solely on that subtraction. “Bring to 100 mL” describes the total solution volume, never an instruction to add 100 mL of solvent.