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.

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

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).

Example and notes

Physiological saline is 0.9 percent w/v sodium chloride: 0.009 × 500 mL = 4.5 g of NaCl made up to 500 mL. For weight-per-volume work, dissolve the solute first and then top up to the mark in a volumetric flask rather than adding 500 mL of water, because the salt itself takes up volume and would otherwise leave the solution too dilute.