Molarity / Normality Calculator

n-factor suggestions · %w/w · %w/v · ppm · reverse modes

Compound quick-reference (optional) Picks only pre-fill the fields — molar mass and n-factor always stay fully editable for any compound

Molar Mass (g/mol)

Mass of Solute (g)

Solution Volume

Unit

Input basis

Molarity (M)

n-factor

Equivalents of Solute (eq)

Solution Volume (mL)

Convert

Value (%w/v)

Solution Density (g/mL) This conversion genuinely needs a density — check the reagent bottle or a data sheet

Value is in ppb (not ppm)

Reverse mode: instead of entering a mass and getting a concentration, enter the concentration you want and get the mass of solute to weigh out. Works from any of the concentration bases this tool handles.

Concentration Basis

Target Molarity (M)

Target Volume (mL)

n-factor ★ Equivalent weight = molar mass ÷ n. Picking a compound above pre-fills this, but it stays fully editable — redox n-factors depend on the reaction.

Solution Density (g/mL)

Reagent Purity / Assay (%) From the bottle label. Below 100% the amount you actually weigh out has to be scaled up so the pure solute still hits the target.

Stock Concentration (M)

Target Molarity (M)

Final Volume (mL)

Result

Choose a mode and calculate to see the concentration, the exact formula applied, and the full working — including which n-factor was used and why

Redox n-factors depend on the reaction medium — the suggested values assume the most common textbook reaction (e.g. KMnO₄ n = 5 in acidic medium, but 3 in neutral and 1 in strongly alkaline), so always confirm against your actual reaction before titration work. ppm and ppb conversions assume a dilute aqueous solution with density ≈ 1 g/mL; they lose accuracy for concentrated or non-aqueous systems. %w/w and %v/v conversions are only as good as the density you enter. Values are for study and lab-prep guidance; verify against your institution's SOP for critical work.

Molarity / Normality Calculator: n-Factor, Percentage Forms, ppm and Reverse Modes

Solution concentration shows up in more forms than just molarity, normality for titrations, percentage by weight or volume on reagent bottles, parts per million for trace analysis and most calculators only handle one or two of these at a time. This tool covers five connected modes. Calculate Molarity directly from mass, molar mass and volume. Calculate Normality either from molarity and an n-factor, or from equivalents directly, with automatic n-factor suggestions for common acids, bases, salts and redox reagents that you can always override, since the correct n-factor for a compound like potassium permanganate genuinely depends on the reaction medium. As a combined normality calculator and equivalent weight calculator, it also converts between %w/w, %w/v, %v/v, and ppm/ppb. Work backward with Mass of Solute reverse mode to find exactly how much to weigh out for a target concentration, accounting for reagent purity. And use Stock Dilution mode to find the volume of a known stock needed for a target diluted molarity. A quick-reference compound list auto-fills molar mass and n-factor for convenience, but both fields always stay fully editable for any compound.

How to Use

This tool has five tabs: Molarity, Normality, % / ppm, Mass of Solute ⇄ and Stock Dilution.

Step 1: Setting up your compound (shared across all modes)

Optionally pick a compound from the Compound quick-reference dropdown, NaOH, HCl, H₂SO₄, KMnO₄ and several others are listed, to auto-fill its molar mass and a suggested n-factor. This is purely a convenience, the Molar Mass field below it always stays fully editable for any compound at all, listed or not.

Step 2: Using Molarity mode

Enter the Mass of Solute in grams and the Solution Volume, choosing mL or L.
Tap Calculate Molarity to get the molar concentration.

Step 3: Using Normality mode

Choose your Input basis: Molarity × n-factor if you already have a molarity figure or Equivalents ÷ volume if you’re working directly from gram equivalents.
If using the molarity basis, enter your Molarity and the n-factor. Picking a compound above suggests a value here, along with a note explaining why, for example that potassium permanganate needs n = 5 in acidic medium but only n = 3 in neutral and n = 1 in strongly alkaline conditions, but you should always confirm this against your actual reaction before relying on it for a titration.
If using the equivalents basis instead, enter your Equivalents of Solute and the Solution Volume.
Tap Calculate Normality.

Step 4: Using % / ppm mode

Select your Conversion direction: %w/v to Molarity, %w/w to Molarity (needs density), %v/v to Molarity (needs solute density), Molarity to %w/v plus ppm, or ppm/ppb to Molarity.
Enter the Value you’re converting from.
If your chosen conversion genuinely needs a solution density, a Solution Density field appears, since this conversion can’t be done without it, check your reagent bottle or a data sheet for this figure.
If converting from ppm, tick “Value is in ppb” if your figure is actually in parts per billion rather than parts per million.
Tap Convert.

Step 5: Using Mass of Solute reverse mode

Switch to the Mass of Solute ⇄ tab. Instead of entering a mass and getting a concentration, this works backward, you tell it the concentration you want, and it tells you the mass to weigh out.
Select your Concentration Basis: Molarity, Normality (uses your n-factor), %w/v, %w/w (needs density), or ppm.
Enter your Target concentration value and Target Volume.
If your basis needs it, enter the n-factor or Solution Density in the fields that appear.
Enter your Reagent Purity / Assay, taken straight from the bottle label. Below 100 percent, the tool scales up the amount you actually weigh so the pure solute content still hits your real target.
Tap Calculate Mass of Solute.

Step 6: Using Stock Dilution mode

Switch to the Stock Dilution tab. Enter your Stock Concentration, the molarity of the solution you already have.
Enter your Target Molarity and Final Volume.
Tap Calculate Dilution to see exactly how much of your stock to use.

Step 7: Exporting your result

Use Print / PDF for a clean printable copy or Copy to paste the figures into your lab notebook.

Key Features

Molarity calculation directly from mass, molar mass and volume
Normality calculation from either molarity and n-factor, or directly from equivalents
Automatic n-factor suggestions for common acids, bases, salts, and redox reagents, always fully editable, with an explanatory note for reaction-dependent cases like permanganate and dichromate titrations
Converts between %w/w, %w/v, %v/v, ppm, and ppb, prompting for density only where the conversion genuinely requires it
Reverse “Mass of Solute” mode that works from any of the five concentration bases and accounts for reagent purity below 100 percent
Stock Dilution mode for finding the exact stock volume needed for a target diluted molarity
Molar mass field never locked, the compound quick-reference list is a convenience only, never a restriction
Full step-by-step working shown for every calculation, including exactly which n-factor was applied and why.

Formula / Logic Used

Molarity

$M = \frac{mass\ /\ molar\ mass}{Volume\ (L)}$

Normality

$N = M \times n\text{-factor}, \qquad \text{or} \qquad N = \frac{Equivalents}{Volume\ (L)}$

The n-factor is the number of reactive units delivered per mole, H⁺ ions for an acid, OH⁻ ions for a base, or electrons transferred in a redox reaction, and the same compound can genuinely need a different n-factor depending on which reaction it’s actually taking part in.

Percentage and ppm Conversions

$M = \frac{\%w/v \times 10}{Molar\ Mass}, \qquad M = \frac{\%w/w \times 10 \times \rho}{Molar\ Mass}$

 $ppm \approx mg/L \ \text{(for a dilute aqueous solution)}, \qquad M = \frac{ppm}{Molar\ Mass \times 1000}$

Reverse Mode: Mass of Solute

 $Mass\ to\ Weigh = \frac{Target\ Concentration \times Volume \times Molar\ Mass}{Purity\ Fraction}$

Dividing by the purity fraction scales the weighed amount up, since a reagent that’s only, say, 95 percent pure needs slightly more mass weighed out for the same amount of actual pure solute to end up in solution.

Stock Dilution

$C_{stock} \times V_{stock} = C_{target} \times V_{final}$

Who Should Use This Tool

Lab technicians and research students preparing titrants, standard solutions, or reagent dilutions who need to move quickly and correctly between concentration units. Also useful for diploma and B.Tech Chemical Engineering and pharmacy students learning molarity, normality and n-factor concepts for their coursework.

Frequently Asked Questions (FAQs)

1. What is the difference between molarity and normality?

Molarity counts moles of solute per litre of solution, while normality counts gram equivalents per litre, which accounts for how many reactive units, H⁺ ions, OH⁻ ions, or electrons, each mole of that solute actually delivers in a specific reaction. For a compound like sulphuric acid with two replaceable H⁺ ions, a 1 M solution is actually 2 N.

2. Why does the n-factor for potassium permanganate change depending on the reaction?

Potassium permanganate can accept a different number of electrons depending on the pH of the reaction medium, 5 electrons in acidic conditions, 3 in neutral conditions, and only 1 in strongly alkaline conditions, which changes its effective n-factor and therefore its normality for the exact same molarity. This tool shows the commonly assumed value with a clear note, but you should always confirm it against your specific titration reaction.

3. How do I convert a percentage concentration like %w/w into molarity?

For %w/v, multiply the percentage by 10 and divide by molar mass. For %w/w, you additionally need the solution’s density, since %w/w is based on total solution mass rather than volume. This tool prompts you for density only for the specific conversions that genuinely require it.

4. How much of a reagent should I actually weigh out if it isn’t 100 percent pure?

Divide your calculated mass by the purity fraction from the bottle label, since a less pure reagent needs proportionally more mass weighed out for the same amount of actual, pure solute to end up dissolved. This tool’s Mass of Solute reverse mode does this scaling automatically once you enter the purity percentage

5. Is ppm the same thing as mg per litre?

For a dilute aqueous solution, where density is close to 1 gram per millilitre, ppm and mg/L are effectively the same number, which is why this approximation is so commonly used in water testing and trace analysis. This approximation loses accuracy for concentrated or non-aqueous solutions, where the actual solution density needs to be accounted for directly.

Related Tools

Chemical Dilution Calculator – for a dedicated C1V1=C2V2 solver, planner and serial dilution table
pH Calculator – check the pH of the acid or base solution you’ve just prepared
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