Percent solution calculator
w/v, v/v or w/w. Fill any two of percent, solute and volume; the third is solved.
w/v, v/v or w/w. Fill any two of percent, solute and volume; the third is solved.
A percent solution states how much solute is in every hundred units of solution, and the letters say which units. w/v (weight per volume) is grams of solute per 100 mL of solution, the usual convention for solids dissolved in water, so 10 % SDS is 10 g in 100 mL.v/v (volume per volume) is millilitres of a liquid per 100 mL of solution, used for liquids mixed with liquids, so 70 % ethanol is 70 mL of ethanol made up to 100 mL. w/w(weight per weight) is grams per 100 g of solution, common in chemistry and on reagent bottles, for example 37 % hydrochloric acid. The three agree only when the solution's density is exactly 1 g/mL.
Worked examples. 500 mL of 10 % w/v SDS needs 10 × 500 ÷ 100 = 50 g of SDS, made up to 500 mL. 250 mL of 70 % v/v ethanol needs 70 × 250 ÷ 100 = 175 mL of absolute ethanol made up to 250 mL with water. 200 g of 20 % w/w sucrose needs 40 g of sucrose and 160 g of water.
Percent w/v and v/v are defined against the volume of the finished solution. Dissolving 50 g of SDS in 500 mL of water gives more than 500 mL and less than 10 %. The right procedure is to dissolve the solute in most of the solvent, then add solvent up to the final volume. The same applies to v/v: 70 mL of ethanol plus 30 mL of water does not make 100 mL, because mixing ethanol and water shrinks the volume slightly, so add water to the 100 mL mark instead.
Because w/v is grams per 100 mL, multiplying by 10 gives grams per litre, and dividing by the molecular weight gives moles per litre. Physiological saline, 0.9 % NaCl with MW 58.44, is 9 g/L or 0.154 M. Enter a molecular weight above to see the molarity of a w/v solution, or use the molarity calculator to work from moles directly. For v/v and w/w solutions the conversion also needs the density, so it is not shown.
| Solution | Type | For 100 mL |
|---|---|---|
| 10 % SDS | w/v | 10 g SDS, water to 100 mL |
| 70 % ethanol | v/v | 70 mL absolute ethanol, water to 100 mL |
| 4 % paraformaldehyde | w/v | 4 g PFA in PBS to 100 mL, dissolved warm |
| 1 % agarose | w/v | 1 g agarose in 100 mL buffer, melted (see the gel calculator) |
| 3 % BSA | w/v | 3 g BSA, buffer to 100 mL |
| 0.5 % Triton X-100 | v/v | 0.5 mL Triton X-100, buffer to 100 mL |
| 0.9 % saline | w/v | 0.9 g NaCl, water to 100 mL |
| 50 % glycerol | v/v | 50 mL glycerol, water to 100 mL |
To dilute one of these stocks to a working strength, use thedilution calculator.
It depends on the type. A 10% w/v solution has 10 g of solute in every 100 mL of final solution; a 10% v/v solution has 10 mL of a liquid in every 100 mL; a 10% w/w solution has 10 g of solute in every 100 g of solution. In biology labs an unlabelled percentage almost always means w/v for solids and v/v for liquids.
Weigh 10 g of solute for every 100 mL you need, dissolve it in less than the final volume of solvent, then add solvent to bring the total volume up to the mark. For 500 mL of 10% SDS that is 50 g made up to 500 mL, not 50 g added to 500 mL.
w/v divides the solute mass by the final volume of solution; w/w divides it by the total mass of solution. They are equal only when the solution has a density of 1 g/mL. For dilute aqueous solutions the difference is small, but for concentrated ones such as 50% glycerol or 70% ethanol it is several percent.
For w/v, molarity = percent × 10 ÷ molecular weight, because percent w/v is g per 100 mL, so ×10 gives g/L. A 0.9% NaCl solution (MW 58.44) is 9 g/L, or 0.154 M. Enter the molecular weight above and the calculator shows it.
Make up to the final volume. A percent w/v or v/v refers to the volume of the finished solution, and adding solute changes the volume. Dissolve in about 80% of the final volume, then top up to the line.