Molarity Calculator
Calculate molarity, moles, volume, solute mass, and dilution with M = n/V and C₁V₁ = C₂V₂. Includes molar, millimolar, micromolar, litre, mL, and µL conversions.
Select a calculation, then enter the known values.
Molarity
Formula used: M = n / V
0.5 M
Molar concentration
500 mM
Millimolar equivalent
0.5 mol
Solute amount
1,000 mL
Final solution volume
Interactive Solution Concentration Visual
A live laboratory view of solute particles, concentration, and final volume.
Step-by-Step Molarity Calculation
Here's exactly how this answer was calculated, one step at a time.
Given: moles = 0.5 mol, volume = 1 L, molarity = 0.5 M
Step 1: Choose the molarity relationship
Molarity is the amount of dissolved solute per litre of final solution.
M = n / VStep 2: Convert the entered units
n = 0.5 mol; V = 1 L; M = 0.5 mol/LStep 3: Substitute the known values
M = 0.5 / 1Step 4: Report the result
Molarity = 0.5 M
Calculated result:
0.5 M
Molarity Calculator: Calculate Molar Concentration Online
This advanced Molarity Calculator calculates molarity, moles, solution volume, grams of solute, and dilution volume in one place. It is designed for chemistry students, laboratory technicians, pharmacists, researchers, teachers, and anyone preparing a chemical solution. Enter values in molar, millimolar, micromolar, litres, millilitres, or microlitres; the calculator converts them consistently before showing the result and written calculation steps.
Molarity is one of the most searched and most useful concentration units in chemistry. A molarity calculator removes repetitive unit conversion while keeping the equation visible. Choose whether you need to calculate M, n, V, preparation mass, or a C1V1=C2V2 dilution. The result panel also gives molar and millimolar equivalents, helping you check whether a solution concentration is realistic for your experiment or homework problem.
What Is Molarity in Chemistry?
Molarity, usually written as M, is the number of moles of solute dissolved in one litre of final solution. A 1.00 M sodium chloride solution contains 1.00 mole of sodium chloride in each litre of solution. The word final is important: the volume is the total solution volume after the solute is dissolved and the solution has been brought to its calibration mark, not the volume of solvent poured in first.
The SI-style expression for molarity is mol/L, although chemists commonly use the shorter symbol M. Molarity connects mass measurements in grams with molecular-scale quantities in moles. Because it is based on solution volume, it is convenient for volumetric glassware, titration, reaction stoichiometry, cell culture, analytical chemistry, and routine laboratory solution preparation.
Molarity Formula: M = n / V
The molarity formula is M = n/V. In this equation, M is molarity in moles per litre, n is the amount of solute in moles, and V is the final volume of solution in litres. For example, dissolving 0.25 mol of glucose and making the final volume 0.50 L produces a concentration of 0.50 M. Always convert millilitres to litres before calculating by hand: 250 mL is 0.250 L.
The formula can be rearranged to answer other common questions. To find moles, use n = M × V. To find volume, use V = n/M. These three forms solve most molarity questions. The calculator selects the correct rearrangement automatically, but showing the formula and converted units remains useful for learning and for checking lab notebook calculations.
How to Calculate Molarity From Grams
If your solute is weighed in grams, first convert grams to moles using its molar mass. The relationship is moles = mass in grams divided by molar mass in g/mol. Then divide those moles by the final solution volume in litres. Combined into one equation, molarity equals mass divided by molar mass and volume: M = mass/(molar mass × volume).
For a sodium chloride example, 5.844 g NaCl has a molar mass of 58.44 g/mol, so it is 0.100 mol. If you dissolve it and make the final volume exactly 1.000 L, the solution is 0.100 M NaCl. The preparation mode in this calculator performs the reverse operation too: choose desired molarity, final volume, and molar mass to find the mass to weigh.
Molarity Unit Conversion: M, mM, µM, and nM
A millimolar solution, mM, is one thousandth of a molar solution: 1 mM = 0.001 M. A micromolar solution, µM, is one millionth of a molar solution: 1 µM = 0.000001 M. Nanomolar, nM, is one billionth of a molar. These compact units are common in biology, pharmacology, buffer preparation, enzyme assays, and trace chemical analysis.
When converting concentration, the numerical direction matters. Multiply molar by 1,000 to obtain millimolar, so 0.025 M equals 25 mM. Divide millimolar by 1,000 to obtain molar. The same factor applies to volume: 1 L equals 1,000 mL and 1 mL equals 1,000 µL. This tool converts inputs internally, reducing a frequent source of thousand-fold laboratory errors.
Dilution Calculator and the C1V1 = C2V2 Formula
A dilution lowers concentration by adding solvent without changing the amount of dissolved solute. The standard dilution formula is C1V1 = C2V2, where C1 is stock concentration, V1 is stock volume used, C2 is desired concentration, and V2 is desired final volume. Use the dilution mode to calculate how much concentrated stock solution to pipette.
For example, to make 100 mL of 0.10 M solution from a 1.00 M stock, V1 = (0.10 × 100)/1.00 = 10.0 mL. Pipette 10.0 mL stock into an appropriate volumetric flask, then add solvent until the total volume reaches 100 mL. Do not add 100 mL of solvent; that would produce more than 100 mL final solution and the concentration would be lower than intended.
How to Prepare a Molar Solution Accurately
To prepare a solution from a solid, calculate the solute mass, weigh it using suitable balance precision, and transfer it quantitatively to a clean volumetric flask. Add roughly two-thirds of the final volume of solvent and swirl until all solute dissolves. Let a warm solution return to calibration temperature before filling to the mark. Finally, add solvent dropwise to the mark and invert the stoppered flask several times to mix thoroughly.
Use the correct grade of reagent, clean glassware, and appropriate personal protective equipment. Hygroscopic solids, hydrates, impure reagents, and volatile liquids can change the actual amount available. For highly accurate standards, account for assay or purity and follow your laboratory's validated method. This calculator gives reliable arithmetic, but a safe preparation also depends on chemical compatibility and good laboratory practice.
Molarity vs Molality, Normality, and Mass Percent
Molarity is moles per litre of solution. Molality is moles per kilogram of solvent, not solution. Molality is often preferred when temperature changes substantially because mass does not expand like volume. Normality expresses reactive equivalents per litre and depends on the reaction being considered, so it is less universal than molarity. Mass percent gives grams of solute per 100 g of total solution.
Choose the unit your procedure or textbook specifies. Do not treat 1 M and 1 m as interchangeable: they may be close for dilute aqueous solutions, but they are defined differently. Likewise, a 10% solution cannot be converted to molarity without knowing molar mass and, for some percentage conventions, solution density. The concentration calculator should be used with clear units written beside every result.
Molarity in Titration and Stoichiometry
In titration, molarity turns measured volume into moles through n = M × V. Once the moles of a known standard are found, a balanced chemical equation gives the reacting mole ratio and lets you determine an unknown concentration. If hydrochloric acid reacts with sodium hydroxide in a 1:1 ratio, equal moles react at the endpoint, though their solution volumes do not need to be equal.
For every stoichiometry calculation, balance the equation before using molarity data. Convert all volumes to litres, calculate moles, apply coefficients as mole ratios, and then convert back to the requested concentration or mass. The advanced modes here are useful for the concentration and preparation parts of that workflow, while the written steps make it easier to identify a unit or ratio error.
Common Molarity Calculation Mistakes
The most common error is using millilitres directly in M = n/V. Since molarity uses litres, a 100 mL solution must be entered as 0.100 L. Another error is dividing by the initial solvent volume rather than final solution volume. A third is overlooking the molar mass unit: grams divided by g/mol gives moles, while milligrams must first be converted to grams.
For dilution, confirm that stock concentration is greater than target concentration; diluting cannot make a weaker stock more concentrated. Use fresh solvent and make up to the final volume precisely. Round only at the end, retain enough significant figures for intermediate work, and use calibrated pipettes or volumetric flasks where precision matters. A quick dimensional check is a strong safeguard: moles divided by litres must end in mol/L.
Applications of Molar Concentration
Molar concentration is central to buffer preparation, pharmaceutical formulation, environmental water testing, clinical chemistry, food analysis, electrochemistry, and biochemistry. A researcher might prepare a 10 mM phosphate buffer, dilute an antibody to 2 µg/mL by a separate mass calculation, or make a 5 µM enzyme substrate solution. In each case, clear concentration units enable repeatable work across people and laboratories.
Industrial and teaching laboratories use molarity because reactions occur between numbers of particles, represented practically by moles. It helps compare substances with different molar masses on an equal chemical basis. Whether you are calculating sodium chloride for saline, glucose for a standard solution, or acid for titration, this molarity calculator provides unit-aware answers, preparation mass, and dilution planning in a single workflow.
Molarity Calculator FAQ and Quick Reference
Use M = n/V to calculate molarity; use n = M×V for moles; and use V = n/M for solution volume. To prepare a solution from a solid, calculate grams as M×V×molar mass. To make a dilution, use C1V1 = C2V2. Keep volume as final solution volume and keep concentration units consistent before multiplying or dividing.
This free online molarity calculator is intended for educational and laboratory-planning calculations. Review the displayed units and steps before acting on a result. For regulated, clinical, or safety-critical work, independently verify the calculation, reagent identity, concentration, purity, and procedure. Correct arithmetic is essential, but it is one part of responsible chemical handling and measurement.
Frequently Asked Questions
What is the formula for molarity?
Molarity equals moles of solute divided by litres of final solution: M = n/V.
How do I calculate molarity from grams?
Divide grams by the molar mass to find moles, then divide by solution volume in litres.
How many mL of 1 M stock make 100 mL of 0.1 M solution?
Use C1V1 = C2V2. The required stock volume is 10 mL, then make up to 100 mL total volume.
Is 1 M equal to 1000 mM?
Yes. One molar equals one thousand millimolar.
What is the difference between molarity and molality?
Molarity is moles per litre of solution, while molality is moles per kilogram of solvent.