Use these nursing scenarios to sanity-check the formula, then load the same values back into the calculator with one click.
Basic Dilution
This is the classic half-strength-from-double-strength dilution problem.
A 25% target is exactly half the 50% stock, so the stock and diluent end up equal here.
Smaller Batch
This example shows a lower target concentration and a smaller final batch size.
This pattern is common when preparing a small-volume bedside or treatment-room solution.
Near-Stock Strength
When the desired concentration is close to the stock concentration, most of the final mixture will be stock solution.
A result like this is a good reminder that solvent volume shrinks as the target concentration approaches the stock strength.
Calculates how much concentrated stock solution (solute) and how much diluent (solvent) to combine to prepare a solution at the desired concentration and volume.
Solute (mL) = (Desired % / Stock %) × Total Volume
Enter the desired solution strength (%), the stock solution strength (%), and the total volume needed. The calculator determines the solute volume (stock solution) and the solvent volume (diluent) required to produce the final solution at the desired concentration.
Prepare 1,000 mL of a 25% solution from a 50% stock solution.
The desired strength can never exceed the stock strength — you cannot concentrate a solution by adding diluent.
Solution reconstitution is the process of diluting a concentrated stock solution to a lower, desired concentration. This is commonly needed for enteral feedings, oral rehydration solutions, topical antiseptics, and irrigation solutions. Always verify the appropriate diluent from the manufacturer's package insert.
The solute is the substance being dissolved (the concentrated stock solution). The solvent is the liquid used to dilute it (such as sterile water or normal saline). Together they make up the final desired solution.
No. You cannot make a solution stronger than the stock solution by dilution alone. The desired strength percentage must be equal to or less than the stock strength. If a higher concentration is needed, a different stock solution must be used.
The appropriate diluent depends on the medication and its intended use. Common diluents include sterile water for injection, normal saline (0.9% NaCl), and bacteriostatic water. Always check the drug manufacturer's package insert for the recommended diluent, as using the wrong one can cause precipitation, reduced potency, or patient harm.
A simple bedside dilution setup is Solute Volume = (Desired Strength ÷ Stock Strength) × Total Final Volume. Once you know the solute volume, subtract it from the desired final volume to find the amount of solvent needed.
Because the total final batch depends on both parts. You are not only calculating how much stock solution to use, you are also ensuring the combined solute and solvent volumes produce the final ordered concentration and total volume.
Always double-check when the final batch is large, when the stock is a high-alert medication, when the diluent must be product-specific, or when the target concentration is close to the stock concentration. Those situations magnify the impact of a simple arithmetic or labeling mistake.
Reference: United States Pharmacopeia (USP) compounding guidance and manufacturer package-insert dilution instructions for stock-solution preparation and reconstitution.