Percent Solution Calculator
Enter a solute amount and a total solution amount to get percent concentration in w/v, w/w, or v/v terms, the units chemistry and pharmacy labs use every day.
🧪 What is a Percent Solution?
A percent solution expresses how much solute is dissolved in a solution as a percentage, using one of three common conventions depending on how the amounts were originally measured: weight/volume (w/v), weight/weight (w/w), or volume/volume (v/v). Each form pairs a solute amount with a total solution amount, then multiplies the ratio by 100 to get a percentage.
Percent solutions appear constantly in real-world chemistry and healthcare. Hospitals prepare 0.9% w/v normal saline for IV fluids, pharmacists formulate 1% w/w hydrocortisone cream, brewers and distillers report alcohol content as % v/v (ABV), and laboratories prepare buffers and reagents at a specified percent concentration. Each of these uses a different measurement convention, which is why this calculator supports all three modes.
A common misconception is that a percent solution is a single, universal unit that converts freely between forms. It does not. % w/v mixes mass and volume units (grams per 100 mL), so it depends on the solution's density and can technically exceed 100%. % w/w and % v/v compare like units to like units (mass to mass, volume to volume), so they behave like ordinary percentages and can never exceed 100%. Confusing the three forms is one of the most common sources of dosing and dilution errors in a lab setting.
This calculator removes that ambiguity by asking which mode you are working in first, then applying the correct formula and showing every step, so the final percentage always matches how the amounts were actually measured.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 — Dilute saline (% w/v)
Dissolve 5 g of NaCl in enough water to make 250 mL of solution.
Example 2 — Sugar solution by mass (% w/w)
Dissolve 15 g of sugar into a solution that weighs 200 g total.
Example 3 — Ethanol dilution (% v/v)
Mix 70 mL of ethanol with enough water to make 200 mL of solution.
❓ Frequently Asked Questions
🔗 Related Calculators
What is a percent solution in chemistry?
A percent solution expresses how concentrated a solute is within a solution, as a percentage. Depending on how the amounts were measured, it can be percent weight/volume (w/v), percent weight/weight (w/w), or percent volume/volume (v/v), each using a different combination of mass and volume units for the solute and the total solution.
What is the formula for percent weight/volume (% w/v)?
% w/v = (mass of solute in grams divided by volume of solution in milliliters) multiplied by 100. For example, dissolving 5 g of salt to make 250 mL of solution gives (5 divided by 250) times 100 = 2% w/v.
What is the formula for percent weight/weight (% w/w)?
% w/w = (mass of solute divided by total mass of the solution) multiplied by 100, with both masses in the same unit. For example, 15 g of sugar dissolved to make 200 g of total solution gives (15 divided by 200) times 100 = 7.5% w/w.
What is the formula for percent volume/volume (% v/v)?
% v/v = (volume of solute divided by total volume of the solution) multiplied by 100, with both volumes in the same unit. For example, 70 mL of ethanol brought up to 200 mL total volume gives (70 divided by 200) times 100 = 35% v/v.
How do I know whether to use w/v, w/w, or v/v?
Match the mode to how you actually measured the solute and the solution. If you weighed the solute in grams and measured the final solution by volume in milliliters, use % w/v. If you weighed both the solute and the whole solution, use % w/w. If you measured both the solute and the whole solution by volume (typically for two liquids), use % v/v.
Is a 5% w/v solution the same concentration as a 5% w/w solution?
Not necessarily. They are only numerically identical when the solution's density is exactly 1 g/mL (approximately true for very dilute aqueous solutions near room temperature). For any solution with a different density, or for w/w versus v/v, the same percentage represents a different actual amount of solute.
Can % w/v exceed 100%?
Yes. Because % w/v compares a mass (grams) to a volume (milliliters), which are different physical quantities, the ratio is not bounded by 100%. Highly concentrated syrups or brines can exceed 100% w/v. % w/w and % v/v, by contrast, compare a part to a whole of the same kind of quantity, so they can never exceed 100%.
How is percent solution different from molarity?
Percent solution (w/v, w/w, or v/v) expresses concentration as a simple mass or volume ratio, with no reference to the solute's molar mass. Molarity expresses concentration in moles of solute per liter of solution, which accounts for molecular weight. Two solutions with the same percent concentration of different solutes can have very different molarities, use the Molarity Calculator to convert when you know the solute's molar mass.
What is a normal saline (0.9% NaCl) solution in grams per liter?
A 0.9% w/v saline solution contains 0.9 g of NaCl per 100 mL of solution, which is equivalent to 9 g per liter. This is the standard isotonic saline solution used in IV fluids and wound irrigation because it closely matches the salt concentration of human blood plasma.
Why can't I directly compare a solute mass to a solution volume in % w/v?
You can, and that is exactly what % w/v measures, it is defined as grams of solute per 100 milliliters of solution, deliberately mixing mass and volume units. This is a practical convenience in labs and clinics, since it is usually easier to measure a final liquid volume with a graduated cylinder than to weigh it, while still weighing the solute precisely on a balance.
How much solute do I need to make a specific percent solution?
Rearrange whichever formula matches your mode. For % w/v, solute mass = (percent divided by 100) times solution volume. For example, to make 500 mL of a 3% w/v solution, you need (3 divided by 100) times 500 = 15 g of solute, then add solvent to bring the total volume to exactly 500 mL.