Calculate w/v%, v/v%, and w/w% solution concentrations. Convert between percent types and determine the amount of solute for any target volume.
Percent solutions are among the most commonly used concentration expressions in laboratories, pharmacies, and clinical settings. The three types — weight/volume (w/v%), volume/volume (v/v%), and weight/weight (w/w%) — each express a different physical relationship between solute and solution, and using the wrong type is a frequent source of errors in solution preparation.
Weight/volume percent (w/v%) is the most common in healthcare and biology: it measures grams of solute per 100 mL of solution. Normal saline is 0.9% w/v NaCl. Dextrose 5% in water (D5W) contains 5 g of dextrose per 100 mL. Volume/volume percent (v/v%) applies to liquid solutes in liquid solutions: 70% ethanol means 70 mL of ethanol per 100 mL of solution. Weight/weight percent (w/w%) is used in industry and for concentrated reagents where solution density is provided.
This calculator handles all three percent types, converts between them using density, calculates the solute amount needed for any target volume, and provides approximate molarity when the molecular weight is known. Preset buttons for common clinical and laboratory solutions make quick work of everyday preparation calculations.
Confusing w/v%, v/v%, and w/w% is one of the most common errors in laboratory and clinical solution preparation. This calculator clarifies which type you're working with and provides the exact amounts needed. This percent solution calculator helps you compare outcomes quickly and reduce avoidable mistakes when making day-to-day care decisions. Use the estimate as a planning baseline and confirm final decisions with a qualified professional when risk is high.
w/v% = (mass_solute_g / volume_solution_mL) × 100. v/v% = (volume_solute_mL / volume_solution_mL) × 100. w/w% = (mass_solute_g / mass_solution_g) × 100. g/L = w/v% × 10. ppm = g/L × 1000.
Result: 0.9% w/v = 9 g/L = 9000 ppm
w/v% = (0.9/100) × 100 = 0.9%. g/L = 0.9 × 10 = 9. ppm = 9 × 1000 = 9000. For 1000 mL, you need 9 g NaCl.
In hospitals, IV fluids are specified as percent w/v: 0.9% NaCl (normal saline), 5% dextrose, 3% hypertonic saline, and 0.45% half-normal saline. Drug concentrations may also be expressed as percent: 1% lidocaine contains 10 mg/mL. Nurses and pharmacists must be fluent in converting between percent and mg/mL (multiply w/v% by 10 to get mg/mL).
When mixing two liquids, the final volume may not equal the sum of the component volumes. Ethanol and water exhibit significant volume contraction: mixing 50 mL ethanol with 50 mL water gives only about 96.3 mL, not 100 mL. This means a "50% v/v" ethanol solution requires adjusting to the mark in a volumetric flask rather than simply combining equal volumes.
In chemical manufacturing, concentrations of stock reagents are typically expressed as w/w% on safety data sheets because this is independent of temperature. Concentrated sulfuric acid is 96% w/w (density 1.84 g/mL). To find its molarity: M = (96 × 1.84 × 10) / 98.08 = 18.0 M. This multi-step conversion from w/w% to molarity is a routine calculation in analytical chemistry.
w/v% uses mass of solute and volume of solution. v/v% uses volume of solute and volume of solution. w/w% uses mass of solute and mass of solution. The choice depends on whether solute and solution are measured by mass or volume.
Healthcare facilities primarily use w/v% for dissolved solids (dextrose, NaCl, KCl) and v/v% for liquid preparations (ethanol, iodine solutions). This keeps planning practical and lowers the chance of preventable errors.
w/v% = w/w% × density of solution. For dilute aqueous solutions (density ≈ 1), they are approximately equal.
10% formalin is 10% v/v formaldehyde solution in water. Since commercial formalin is 37% formaldehyde, "10% formalin" is actually about 3.7% formaldehyde. This is a common source of confusion in histology.
By convention, 70% ethanol for disinfection is v/v: 70 mL of ethanol per 100 mL of solution. Note that mixing 70 mL ethanol with 30 mL water gives less than 100 mL due to volume contraction.
Weigh 4.5 g of NaCl (0.9% of 500 = 4.5 g), dissolve in water, and bring to 500 mL total volume in a volumetric flask.