Use this concentration calculator to find molarity, dilution amounts, or convert percent concentration to molarity with clear unit and density guidance.
Advanced options
How to use our Concentration Calculator
- Choose a task in What do you want to calculate: molarity, dilution, or percent concentration to molarity.
- Enter the visible inputs only, and make sure labels match what you have, especially Solution volume (L) versus Final volume (mL) and the correct Percent type.
- Click Calculate to see the main answer first, then the support results such as Moles of solute, Mass per liter, Stock volume needed, or Solvent to add.
- Sanity-check the result: if Stock volume needed is bigger than Final volume (mL), or if the Note says density is missing, fix those inputs before using the answer.
Definitions
Molarity (M): Moles of solute in 1 liter of final solution.
Molar mass (g/mol): The mass of 1 mole of a substance.
Solute mass (g): The grams of dissolved substance you put into the solution.
Solution volume (L): The final total volume of the mixed solution, not just the solvent.
Stock concentration: The concentration of the starting solution before dilution.
Final volume (mL): The total volume you want after dilution is complete.
% w/v: Grams of solute per 100 mL of solution.
% w/w: Grams of solute per 100 g of solution.
% v/v: mL of solute per 100 mL of solution.
Density (g/mL): Mass per milliliter. It is needed when a percent value must be connected to volume or mass.
Mass per liter (g/L): How many grams of solute are present in each liter of final solution.
Common mistakes and quick fixes
Mistake: Entering water added instead of the final total in Solution volume (L) .
Fix: Use the finished total solution volume after everything is mixed.
Mistake: Using the wrong unit family in dilution mode, such as thinking Stock concentration in M can be compared to a target written as ppm.
Fix: Keep Stock concentration unit matched to the concentration family you want to dilute within.
Mistake: Choosing the wrong Percent type for a label that says % w/w, % w/v, or % v/v.
Fix: Match Percent type exactly to how the concentration was given before trusting Calculated concentration .
Mistake: Leaving out Solution density (g/mL) for % w/w or Solute density (g/mL) for % v/v.
Fix: Enter the required density for that percent type, or switch to the percent type that actually matches your data.
Mistake: Typing a very small or very large Molar mass (g/mol) by accident.
Fix: Recheck the compound formula and confirm that Moles of solute and Mass per liter look reasonable for your sample.
Mistake: Asking for a stronger target than the stock in dilution mode, so Target concentration is greater than Stock concentration .
Fix: Use a more concentrated stock, lower the target, or make the solution another way because the shown dilution is not feasible.
Limitations & Key Assumptions / Boundary Conditions
- Dilution mode uses the simple relation C1V1 = C2V2, so the stock and target must stay in the same concentration family.
- Percent-to-molarity mode accepts percent values greater than 0 and up to 100 only.
- % w/w to molarity needs Solution density (g/mL) because mass percent alone does not tell you the solution volume.
- % v/v to molarity needs Solute density (g/mL) because solute volume must be converted to solute mass before finding moles.
- For % v/v, the calculation assumes the entered solute density is for the pure solute and uses the usual classroom conversion approach.
- The calculator ignores hidden fields in other modes, so only the visible inputs affect the active result.
- Real lab mixtures can differ slightly from ideal classroom calculations because measured density, temperature, purity, and volume changes on mixing can change the final concentration.
Methodology
How the calculator works
The calculator uses one formula set for each mode and reads only the inputs shown for that mode.
Molarity from mass and volume
First find moles from mass and molar mass, then divide by the final solution volume.
M = (mass_g / molar_mass_g_per_mol) / volume_L
moles = mass_g / molar_mass_g_per_mol
mass per liter = mass_g / volume_L
Mini-example: if Solute mass (g) is 5.844, Molar mass (g/mol) is 58.44, and Solution volume (L) is 0.250, then moles = 5.844 / 58.44 = 0.100 mol and molarity = 0.100 / 0.250 = 0.400 M. Mass per liter is 5.844 / 0.250 = 23.376 g/L.
Dilution mode
This mode uses the standard dilution equation. The concentration unit family must stay the same on both sides.
C1 x V1 = C2 x V2
stock volume needed = (target_conc x final_volume) / stock_conc
solvent to add = final_volume - stock volume needed
Mini-example: if Stock concentration is 1.00 M, Target concentration is 0.100 M, and Final volume (mL) is 100, then stock volume needed = (0.100 x 100) / 1.00 = 10 mL. Solvent to add = 100 - 10 = 90 mL.
Percent concentration to molarity
The correct formula depends on the selected Percent type.
% w/v: M = (percent x 10) / molar_mass_g_per_mol
% w/w: M = (percent x density_solution_g_per_mL x 10) / molar_mass_g_per_mol
% v/v: M = (percent x density_solute_g_per_mL x 10) / molar_mass_g_per_mol
The factor 10 converts a per-100-mL basis to a per-liter basis because 1 L = 1000 mL, which is ten groups of 100 mL.
Mini-example for % w/v: if Percent concentration (%) is 5 and Molar mass (g/mol) is 58.44, then M = (5 x 10) / 58.44 = 0.8556 M. That also means 50 g/L and 0.8556 mol in each liter.
Output logic
Calculated concentration is the main answer in molarity and percent-conversion modes. In dilution mode, the most helpful primary prep number is Stock volume needed, followed by Solvent to add.
Moles of solute is shown for molarity and percent-conversion modes. In percent-conversion mode, it is the number of moles represented by 1 liter of solution, so its value matches the molarity number.
Mass per liter is shown as a quick reasonableness check because it tells you how many grams of solute are in 1 liter of final solution.
Assumptions and limits
The equations follow standard classroom concentration relationships for molarity, dilution, and common percent forms [1]. Results can differ from a real prepared solution if density values are off, if the solute is impure, or if volumes change noticeably during mixing.