Percent Solution Calculator
Prepare % w/w, % w/v and % v/v solutions like a lab tech: enter any two values and get the solute mass, solvent amount, or final concentration — plus % w/w ↔ % w/v density conversion and a percent ↔ ppm ↔ ppb converter.
Percent solution calculator
Pick a percent type, choose what to solve for, and enter the two values you know. Results include the solvent you need and the full working.
Tip: results update live as you type.
Density conversion: % w/w to % w/v
Percent w/w and percent w/v are only equal when the solution density is 1.00 g/mL. Enter the density to convert exactly.
Percent to ppm to ppb converter
Type in any one box; the other two update instantly. Exact by mass, and valid for dilute water-based solutions where 1 mL weighs about 1 gram.
Reference: 1% = 10,000 ppm = 10,000,000 ppb.
Worked examples: how to make a percent solution
Example 1 — 5% w/v NaCl, 500 mL: 5% w/v means 5 g per 100 mL, so 500 mL needs 25 g of NaCl. Weigh 25 g, dissolve in water, bring to exactly 500 mL.
Example 2 — 70% v/v ethanol, 1 L: 70% v/v means 70 mL per 100 mL, so 1000 mL needs 700 mL of ethanol. Measure 700 mL ethanol, add water to a final volume of 1 L (top up to the mark — volumes are not perfectly additive).
When to use % w/w vs % w/v vs % v/v
| Type | Definition | Use it when… | Typical example |
|---|---|---|---|
| % w/w | g solute per 100 g solution | you weigh everything; temperature-independent; commercial reagents | 37% w/w hydrochloric acid |
| % w/v | g solute per 100 mL solution | a solid is dissolved and brought to a final volume | 0.9% w/v normal saline, 5% w/v NaCl |
| % v/v | mL solute per 100 mL solution | both solute and solvent are liquids | 70% v/v ethanol disinfectant |
Three rules that prevent bad batches
1. % w/v and % v/v use the final volume. Dissolve first, then top up to the mark in a volumetric flask or graduated cylinder — do not just add the nominal solvent volume, because volumes are not strictly additive.
2. % w/w never needs a density. Mass is mass at any temperature, which is why concentrated acids are sold as % w/w.
3. Converting between types needs the density. % w/v = % w/w × density (g/mL). For dilute water solutions the density is close to 1.00 g/mL and the numbers nearly match.
What this tool covers
Frequently asked questions
What is a percent solution in chemistry?
A percent solution expresses concentration as parts of solute per 100 parts of solution. The three common types are percent weight per weight (% w/w), percent weight per volume (% w/v), and percent volume per volume (% v/v). Which one you use depends on whether your solute and solvent are solids or liquids.
How do I make 500 mL of a 5% w/v NaCl solution?
A 5% w/v solution contains 5 grams of solute per 100 mL of solution. For 500 mL you need 5 divided by 100 times 500, which is 25 grams of NaCl. Weigh 25 grams of NaCl, dissolve it in water, then add water until the total volume reaches exactly 500 mL.
How do I make 1 liter of 70% v/v ethanol?
A 70% v/v solution contains 70 mL of solute per 100 mL of solution. For 1000 mL you need 70 divided by 100 times 1000, which is 700 mL of ethanol. Measure 700 mL of ethanol and add water until the final volume is 1 liter. Volumes are not perfectly additive, so always top up to the final mark instead of adding exactly 300 mL of water.
What is the difference between % w/w, % w/v, and % v/v?
Percent w/w is mass of solute divided by mass of solution times 100, used when both parts are weighed. Percent w/v is grams of solute per 100 mL of solution, the standard for dissolving a solid in a liquid. Percent v/v is mL of solute per 100 mL of solution, used for liquid in liquid mixtures. Use the calculator above to work with any of the three.
When should I use % w/w instead of % w/v?
Use % w/w when you weigh both the solute and the solution, for example solid mixtures or concentrated commercial reagents like acids, because mass does not change with temperature. Use % w/v when you dissolve a solid and bring the mixture to a final volume in a volumetric flask, which is the usual lab and pharmacy routine. Use % v/v for liquid in liquid mixtures such as alcohol solutions.
How do you convert % w/w to % w/v?
Multiply the % w/w value by the density of the solution in g per mL. For example, a 37% w/w solution with a density of 1.19 g per mL equals 37 times 1.19, which is 44.03% w/v. To go the other way, divide % w/v by the density. Enter the density in the converter above for an exact conversion.
How many ppm is 1 percent?
One percent equals 10,000 ppm, and one percent equals 10,000,000 ppb. So 250 ppm is 0.025 percent, and 500 ppb is 0.00005 percent. This holds exactly by mass, and for dilute water based solutions where 1 mL weighs about 1 gram. Use the converter panel above to convert between percent, ppm, and ppb.
How do I calculate how much solvent I need?
Subtract the solute from the total solution. For 200 grams of a 10% w/w solution you need 20 grams of solute, so the solvent is 200 minus 20, which is 180 grams. For volume based solutions the solvent volume is approximately the final volume minus the solute volume. The calculator shows the solvent amount automatically with every result.
What percent is normal saline?
Normal saline is 0.9% w/v sodium chloride, which means 0.9 grams per 100 mL. To make 1 liter you need 0.9 divided by 100 times 1000, which is 9 grams of NaCl dissolved and brought to a final volume of 1000 mL.
I dissolved 15 g of salt to make 300 g of solution. What is the concentration?
Divide the solute by the total and multiply by 100: 15 divided by 300 times 100 equals 5% w/w. Enter any two of the three values in the calculator and it solves for the third.
Is 5% w/v the same as 5% w/w?
Only when the solution density is exactly 1.00 g per mL. For a solution with density 1.05 g per mL, 5% w/v divided by 1.05 equals about 4.7619% w/w. For dilute water solutions the difference is small, but for dense solutions such as concentrated acids it is large, so convert with the density when accuracy matters.
Can this calculator dilute a stock solution?
This tool covers preparing a percent solution from scratch: % w/w, % w/v, and % v/v. Diluting an existing stock solution to a lower concentration uses different math, C1V1 equals C2V2, and belongs to a dedicated solution dilution calculator. The worked examples above assume you start from pure solute and solvent.
How do I convert ppb to percent?
Divide ppb by 10,000,000. For example, 500 ppb divided by 10,000,000 equals 0.00005 percent. To convert percent to ppb, multiply by 10,000,000 instead. The converter panel above does all three directions instantly.
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