Pharmaceutical Chemistry

Percentage Solution Calculator

Works out solute, solvent, final solution amount or strength for w/v, v/v and w/w percentage solutions.

Solute Amount

Enter the percentage and the final solution volume.

Inputs

Weight/Volume (w/v): Mass of solute per volume of solution

Percentage (%)

The strength you want, as g per 100 mL.

Total solution volume

Final volume after making up — solute plus solvent, not solvent alone.

Round to

Decimal places in the result.

Try a common laboratory solution

Sets the type and percentage and switches to Total Solution — then enter how much solute you have.

Common percentage conversions

How much solute is in 100 parts of solution at each strength.

Percentage	w/v (g/100mL)	v/v (mL/100mL)	w/w (g/100g)	Common Use
0.1%	0.1g	0.1mL	0.1g	Dilute standards
0.5%	0.5g	0.5mL	0.5g	Agar plates
1%	1g	1mL	1g	Staining solutions
5%	5g	5mL	5g	Blocking buffers
10%	10g	10mL	10g	SDS-PAGE gels
20%	20g	20mL	20g	Sugar solutions
50%	50g	50mL	50g	Glycerol stocks

% (w/v) = (solute weight / solution volume) × 100

% (v/v) = (solute volume / solution volume) × 100

% (w/w) = (solute weight / solution weight) × 100

Solute = (% / 100) × solution · Solution = solute / (% / 100) · Solvent = solution − solute

The solute is the substance being dissolved, the solvent is what it is dissolved in (usually water), and the solution is the finished mixture of both. A percentage always refers to the total solution, so a 0.9% (w/v) saline holds 0.9 g of NaCl in every 100 mL of finished solution — not in 100 mL of water.

The calculator uses the numbers exactly as entered and does not convert between units, so enter solute and solution in matching units (g with mL for w/v, mL with mL for v/v, g with g for w/w).

Worked example: sodium citrate anticoagulant for a haematology practical

Blood samples for an ESR practical are collected into 3.8% w/v trisodium citrate. You need 150 mL of the solution. How much trisodium citrate do you weigh? (Illustrative values.)

Percentage type: Weight/Volume (w/v)
Solve for: Solute Amount
Percentage: 3.8 %
Total solution volume: 150 mL (solute unit g)

Meaning of the strength
3.8% w/v = 3.8 g of solute in every 100 mL of finished solution
Write the formula
Solute (g) = (% ÷ 100) × solution volume (mL)
Substitute
Solute = (3.8 ÷ 100) × 150 = 0.038 × 150
Result
Solute = 5.7 g

Weigh 5.7 g of trisodium citrate, dissolve it in less than 150 mL of water, then make up to 150 mL.

The calculator prints 5.7 g with the instruction to make up to a final volume of 150 mL. The percentage refers to the finished solution, so the water is whatever it takes to reach 150 mL — not 150 mL of water. Check which salt form your method means: the dihydrate and anhydrous salts differ in mass.

Common mistakes

Calculating the percentage on the solvent instead of the whole solution: 3.8 g + 150 mL of water is not 3.8% w/v. Make up to the final volume (w/v, v/v) or final mass (w/w).

Picking units that do not match the definition. This calculator does not convert, so for w/v enter grams with millilitres; 0.9% of a solution entered as 1 L gives 0.009 g instead of the correct 9 g — enter 1000 mL.

Mixing up w/v and w/w for semi-solids and concentrated acids: a 10% w/w ointment means 10 g per 100 g of ointment, and the base must be weighed, not measured by volume.

Assuming v/v volumes add up: 70 mL of ethanol plus 30 mL of water gives slightly less than 100 mL, so 70% v/v ethanol is made by making up 70 mL of ethanol to 100 mL.

Confusing percentage with ratio strength: 1 in 1000 is 0.1%, and 1:1000 adrenaline is 1 mg/mL — not 1%.

Assumptions and limitations

The page uses the numbers exactly as entered and applies no unit conversion, so the answer is only correct when solute and solution units match the percentage type.

For w/v and v/v solutions the 'Solvent Amount' result is solution − solute, which assumes volumes are additive and, for w/v, subtracts a mass from a volume. Use it only as a rough guide; in practice dissolve and make up to volume.

A percentage says nothing about osmotic or molar strength. Two 1% w/v solutions of different drugs contain different numbers of molecules.

Guide: Dilution and Concentration CalculationsThe concept in full, with practice questions.Dilution Calculator (C₁V₁ = C₂V₂)Dilute a percentage stock to a weaker strength.Molarity CalculatorWhen the method asks for mol/L rather than a percentage.Isotonicity CalculatorCheck whether a % w/v eye drop or injection is isotonic.

References

Stockton SJ. Stoklosa and Ansel's Pharmaceutical Calculations. 16th ed. Philadelphia: Wolters Kluwer; 2021.
Sinko PJ, editor. Martin's Physical Pharmacy and Pharmaceutical Sciences. 8th ed. Philadelphia: Wolters Kluwer; 2023.

Common questions

w/v is grams of solute per 100 mL of solution (solids in liquids, e.g. saline). v/v is millilitres of solute per 100 mL of solution (liquids in liquids, e.g. 70% ethanol). w/w is grams of solute per 100 g of solution (both weighed, e.g. ointments and concentrated acids).

Volumes are not always additive — many solutes change the volume when they dissolve, and in w/v you subtract a mass from a volume. In practice you dissolve the solute and make up to the final volume, rather than measuring the solvent separately. The solvent figure is only a rough guide outside w/w.

Yes. This calculator does not convert units — it treats the numbers as entered and labels the answer with the unit you picked. For a true percentage, enter solute in g and solution in mL (w/v), mL and mL (v/v), or g and g (w/w).

No — the solute cannot occupy more than the whole solution. A w/v figure can exceed 100% for very soluble solids, since mass and volume are different quantities.

About percentage solutions

A percentage solution states how much solute is in every 100 parts of the finished solution. Which “parts” depends on the type.

Weight/Volume (w/v)%

Mass of solute (g) per 100 mL of solution. Common for solids dissolved in liquids. Example: 1% (w/v) NaCl = 1g NaCl in 100mL water.

Volume/Volume (v/v)%

Volume of solute (mL) per 100 mL of solution. Common for liquids mixed with liquids. Example: 70% (v/v) ethanol = 70mL ethanol + 30mL water.

Weight/Weight (w/w)%

Mass of solute (g) per 100g of solution. Used when both components are weighed. Example: 10% (w/w) NaOH = 10g NaOH + 90g water.

Use it when

Preparing saline, glucose, ethanol or stain solutions at the bench

Checking the strength of a solution you have already made

Scaling a percentage formula to a different final volume or mass

Important notes

Always add solute to solvent, not vice versa (especially for concentrated acids/bases)

For w/v solutions, final volume is measured after dissolution

For w/w solutions, temperature affects density and weight measurements

Some solutes have significant volume change upon dissolution

No unit conversion is applied — numbers are used as entered, so pick matching units (g with mL, mL with mL, g with g)

Prepared by the PharmaWallah student team. Verify results with your textbook or instructor. Report an error · Editorial policy