Percentage Solution Calculator

Calculate the concentration of a percentage solution (% w/v, % w/w, or % v/v), or work out how much solute you need to prepare a solution at a target percentage — for reagent, stain, and media preparation.

Solution details

Solution type

Common for dissolving a solid reagent (e.g. NaCl, KOH) in a liquid.

Amount of solute

Total amount of solution

Concentration

–

% w/v and % w/w figures assume aqueous solutions at room temperature unless your protocol states otherwise. Always confirm reagent grade and safety data before preparing lab solutions.

Common Lab Percentage Solutions (tap to load)

Normal Saline

0.9% w/v

Isotonic diluent, wet mounts

Neutral Buffered Formalin

10% w/v

Tissue fixation

Ethanol / Isopropanol

70% v/v

Disinfection, dehydration

Hydrogen Peroxide

3% v/v

Disinfectant, catalase test

Potassium Hydroxide

20% w/v

Fungal skin/nail wet mount

Crystal Violet

1% w/v

Gram stain reagent

Formulas

% w/v = (Weight of solute in g ÷ Volume of solution in mL) × 100 % w/w = (Weight of solute in g ÷ Weight of solution in g) × 100 % v/v = (Volume of solute in mL ÷ Volume of solution in mL) × 100

About percentage solutions

A percentage solution expresses how much solute is present per 100 parts of the total solution. Laboratories use three conventions depending on the physical states involved: % w/v for a solid dissolved in a liquid (the most common form for reagents and stains), % w/w for two solids or a solid in a semi-solid, and % v/v for a liquid diluted in another liquid. The unit is always parts per 100, but what "part" means (grams or mL) changes with the convention — which is why matching the right type to your reagent matters.

Preparing a solution from a target percentage

For % w/v: weigh the solute, dissolve it in less than the final volume of solvent, then add solvent up to the total final volume — do not simply add the solute to the full final volume of solvent, as the solute itself displaces some volume.
For % w/w: weigh the solute and the diluent separately so their combined weight equals the target total weight.
For % v/v: measure the solute volume, then add diluent up to the final total volume using a volumetric flask or cylinder.

Notes and limitations

This calculator assumes ideal mixing with no significant volume contraction or expansion; for precise reagent work, always follow your lab's validated SOP.
For serial dilutions from a stock solution (C₁V₁ = C₂V₂), use a dedicated dilution calculator — this tool is for preparing a solution from pure solute, not diluting an existing stock.
Always label prepared reagents with concentration, preparation date, and expiry per your quality management system (e.g. ISO 15189).