Percentage Concentration to Molarity
Convert percentage concentration (% w/v, % w/w) to molarity (mol/L) using density and molar mass. Free online chemistry concentration converter for lab work, teaching, and research.
About This Calculator
The Percentage Concentration to Molarity Calculator converts a solution's percentage concentration (w/v% or w/w%) to molarity (mol/L or M) using the solution density and molar mass. This conversion is essential in chemistry labs for preparing solutions, performing titrations, and scaling reactions from concentrated stock solutions.
The formula used is: Molarity (mol/L) = (Percentage concentration × Density × 10) / Molar mass. The factor of 10 converts density from g/mL to g/L. For example, 37% hydrochloric acid with density 1.19 g/mL and molar mass 36.46 g/mol yields (37 × 1.19 × 10) / 36.46 = 12.08 M.
Select a common substance from the dropdown to auto-fill typical density and molar mass values, or enter custom values for any chemical. The calculator supports all acids, bases, salts, and organic compounds — just provide the correct density for your specific solution concentration.
Regional Notes
Worldwide: Percentage concentration to molarity conversion is a universal chemistry calculation. Use the density value for your specific solution (temperature-dependent) for accurate results. Common reference densities are provided for standard laboratory-grade chemicals.
Frequently Asked Questions
What is the formula to convert percentage concentration to molarity?
Molarity (mol/L) = (Percentage concentration × Density × 10) / Molar mass. Density must be in g/mL, molar mass in g/mol. For example, 37% HCl (density 1.19 g/mL, molar mass 36.46 g/mol) gives (37 × 1.19 × 10) / 36.46 = 12.08 M.
How do I convert molarity back to percentage concentration?
Percentage concentration = (Molarity × Molar mass × 100) / Density. This reverses the formula: multiply molarity by molar mass and 100, then divide by density to get the percentage concentration.
What is the difference between w/v% and w/w%?
Weight by volume (w/v%) is grams of solute per 100 mL of solution. Weight by weight (w/w%) is grams of solute per 100 g of solution. This calculator works with both when you use the correct density — use solution density for w/v% and solute density for w/w%.
Why do I need the density of the solution?
Density bridges the gap between percentage concentration (mass/mass or mass/volume) and molarity (moles/volume). Without density, you cannot convert between these units because the same percentage can correspond to different molarities depending on solution density.
What is the molarity of concentrated hydrochloric acid (37% HCl)?
Concentrated HCl at 37% (w/w) has a density of approximately 1.19 g/mL and molar mass 36.46 g/mol. Using the formula: (37 × 1.19 × 10) / 36.46 = 12.08 M. This is the standard concentrated HCl used in laboratories worldwide.
Is this calculator free to use?
Yes, this percentage concentration to molarity converter is completely free to use with no registration required. Your inputs are saved in the URL for easy sharing.
Can I share my calculation results?
Yes, all input values are saved in the URL parameters. You can copy the URL to share your exact calculation with colleagues or bookmark it for later reference.
How accurate are the calculated molarity values?
Molarity is calculated to 4 decimal places using the standard formula. Accuracy depends on the precision of your input values for percentage concentration, density, and molar mass. Use precise density values from chemical reference tables for best results.