What does a percent solution mean?

A percent solution states how much solute is present per 100 parts of solution. A 5 percent w/v solution holds 5 grams of solute in every 100 mL of finished solution, while 5 percent v/v holds 5 mL of one liquid per 100 mL of mixture.

What is the difference between w/v, w/w, and v/v?

Weight-per-volume (w/v) measures grams of solute per mL of solution; weight-per-weight (w/w) measures grams per gram; and volume-per-volume (v/v) measures mL per mL. Mixing them up changes the answer, so always match the convention to the material.

How much solute do I need for a target percentage?

Multiply the percentage (as a fraction) by the total solution amount. For 0.9 percent w/v saline in 500 mL you need 0.009 x 500 = 4.5 g of sodium chloride. The tool does this automatically when you solve for solute.

Do I add solvent to the final volume?

For w/v you dissolve the solute then bring the solution up to the final volume in a volumetric flask, because the dissolved solute itself occupies space. Simply adding that volume of solvent would over-dilute the solution.

Is 1 percent w/v the same as 10 g/L?

Yes. One percent w/v is 1 g per 100 mL, which equals 10 g per 1000 mL, or 10 g/L. This is a handy conversion when a protocol lists a concentration in g/L but your balance and flask work in percentage terms.

What is the Percent Solution Calculator (w/v, w/w, v/v)?

Convert between mass, volume, and percentage for weight-per-volume, weight-per-weight, and volume-per-volume solution preparation. Solve for solute amount, total volume, or percentage. For pharmacy, chemistry labs, and food science. It runs free in your browser on Gera Tools, with nothing uploaded.

Percent Solution Calculator (w/v, w/w, v/v)

Name: Percent Solution Calculator (w/v, w/w, v/v)
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Percent solutions express concentration as parts of solute per 100 parts of solution. This calculator handles the three common conventions — weight-per-volume, weight-per-weight, and volume-per-volume — and solves for whichever quantity you are missing.

How it works

Each percentage type uses the same shape with different units:

w/v %  =  solute mass (g)   / solution volume (mL) × 100   (g per 100 mL)
w/w %  =  solute mass (g)   / solution mass   (g)  × 100
v/v %  =  solute volume(mL) / solution volume (mL) × 100

Rearranging lets you solve for any one unknown. To find the solute needed, solute = (percentage / 100) × total. To find the total that a fixed amount of solute produces, total = solute / (percentage / 100).

Which type should you use?

Choosing the right percentage convention is not just a formality — the numbers differ, and mixing them up leads to wrong concentrations:

w/v (weight per volume) is the standard in pharmacy, clinical labs, and most biology protocols. A percentage of a solid dissolved in a liquid (saline, glucose in water, drug in buffer) is almost always w/v. It is convenient because you weigh the solute and measure the final volume in a volumetric flask.
w/w (weight per weight) appears in food science, agriculture, and industrial chemistry where mixing two solids or concentrated mixtures by mass is more practical than measuring volume. Percentage by mass is also independent of temperature — volume can expand with heat, but mass stays fixed.
v/v (volume per volume) is the convention for liquid-in-liquid mixtures: alcohol concentrations in beverages (ethanol in water), solvent mixtures in chromatography, or diluting concentrated acid. Note that volumes are not always additive — 50 mL ethanol + 50 mL water does not reliably give 100 mL due to molecular interactions.

Worked examples

Pharmacy — 5% w/v glucose in 500 mL: Solute = (5/100) × 500 mL = 25 g of glucose made up to 500 mL in a volumetric flask.

Food science — 10% w/w salt brine in 2 kg water: Solute = (10/100) × 2,000 g = 200 g of salt; total solution mass = 200 + 2,000 = 2,200 g.

Lab solvent — 70% v/v ethanol: In 1,000 mL final volume: ethanol = (70/100) × 1,000 = 700 mL, then top up to 1,000 mL with water (not add 300 mL, because mixing contracts the total volume slightly).

Preparation tips

For w/v solutions always dissolve the solute first, then bring the solution to the final target volume using a volumetric flask. Never add the target volume of solvent directly — the dissolved solute displaces liquid and you will under-fill. For w/w, weigh both components and mix; this is the safest approach when temperature stability matters. For v/v, measure both liquids, add the denser one to the less dense to control exothermic mixing (especially with concentrated acids or alcohols).