Pick what you are solving for
Molarity, moles, volume, mass to prepare a solution, or dilution. The selected mode shows only the fields that equation needs, and the formula it will use is printed under the tabs.
Calcolatore Molarità Online
Calcolatore di molarità online facile e preciso. Trova la concentrazione molare delle tue soluzioni chimiche inserendo massa e volume.
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What do you want to solve for?
Pick the unknown, enter the values you already have, and the formula, the unit conversion and the worked steps appear on the right. The arithmetic runs in your browser — no AI model decides the number.
Calculator mode
Solving for with
g/mol
Fill in any three boxes and leave the one you are solving for empty — the empty box is the unknown and is highlighted below.
Results update as you type — the button is only there if you prefer to press one.
Try a worked example
Step-by-step working
Written out so you can hand in the working, not just the number. Check each line against your own arithmetic before you copy it.
This is a free molarity calculator: choose what you are solving for — molarity, moles, volume, the mass to weigh out, or a dilution — enter the values you know, and the answer appears with the formula, the unit conversion and the substituted arithmetic written out. Volume works in L, mL or µL and is converted to litres for you. The math is computed in your browser from fixed chemistry formulas, so no AI model is deciding the number.
How to use the molarity calculator
Enter the values you know
Type the numbers and choose the units from the dropdowns — mL and L both work for volume. In dilution mode leave the box you are solving for empty; it is highlighted as the unknown.
Read the worked steps
The answer updates as you type, with the formula, the given values, any unit conversion, and the substituted calculation on separate lines — the working you can check against your own.
When students use a molarity calculator
The same equation shows up in three different places in a chemistry course, and the calculator covers all of them.
Homework and problem sets
Concentration questions rarely stop at one division — you convert millilitres to litres, sometimes grams to moles, then divide. Checking each of those lines separately is how you find where a wrong answer went wrong.
Preparing a solution in the lab
Before a titration or a buffer you need a mass on a balance, not a concentration. Target molarity times target volume gives moles; moles times molar mass gives the grams to weigh out.
Exam revision
Rearranging M = n / V under time pressure is the skill being tested. Working through the steps here, then covering them and redoing the problem by hand, is what makes the rearrangement automatic.
Units the molarity calculator accepts
Enter values in the units your question uses — everything is normalised to litres and moles before the arithmetic, and the conversion is printed in the working.
Volume and amount
Volume is the field that trips students up: M = n / V is defined with V in litres, so a millilitre reading has to be divided by 1000 first. The calculator shows that line rather than hiding it.
- Volume — L, mL, µL
- Amount — mol, mmol
- 250 mL = 0.25 L
- 500 mmol = 0.5 mol
Concentration and mass
M and mol/L are two spellings of one unit, so either can be entered. Molar mass is always g/mol, and the mass answer is reported in grams with the milligram equivalent alongside.
- Concentration — M, mol/L, mmol/L
- Molar mass — g/mol
- Mass answer — g (and mg)
- 0.5 mol/L = 0.5 M
Come funziona
- Inserisci i grammi di soluto e il peso molecolare.
- Indica il volume finale della soluzione in litri.
- Clicca su "Calcola Molarità".
- Ottieni la concentrazione molare espressa in mol/L (M).
Molarity calculator examples
Every example below is computed by the same code the calculator runs, so the numbers and the working match exactly what you get when you type your own values in.
Find molarity from moles and volume
You dissolve 0.50 mol of NaCl in enough water to make 1.00 L of solution. What is the molarity?
- Formula
- M = n / V
- Given
- n = 0.50 mol, V = 1.00 L
- Calculation
- M = 0.5 / 1 = 0.5 mol/L
- Answer
- 0.5 M
Find the moles of solute
How many moles of solute are in 0.25 L of a 2.0 M solution?
- Formula
- n = M × V
- Given
- M = 2.0 M, V = 0.25 L
- Calculation
- n = 2 × 0.25 = 0.5 mol
- Answer
- 0.5 mol
Dilute a stock solution
You dilute 100 mL of a 1.0 M stock solution to a final volume of 500 mL. What is the new concentration?
- Formula
- M₁ × V₁ = M₂ × V₂
- Given
- M₁ = 1.0 M, V₁ = 100 mL = 0.1 L, V₂ = 500 mL = 0.5 L
- Unknown
- M₂ — the box you left empty
- Calculation
- M₂ = (M₁ × V₁) / V₂ = (1 × 0.1) / 0.5 = 0.2 mol/L
- Answer
- M₂ = 0.2 mol/L
Find the volume that holds a given amount
What volume of a 2.0 M solution contains 0.50 mol of solute?
- Formula
- V = n / M
- Given
- n = 0.50 mol, M = 2.0 M
- Calculation
- V = 0.5 / 2 = 0.25 L
- Answer
- 0.25 L (250 mL)
Find the mass to prepare a solution
How many grams of NaCl (molar mass 58.44 g/mol) do you weigh out for 500 mL of 0.10 M solution?
- Formula
- n = M × V, then mass = n × molar mass
- Given
- M = 0.10 M, V = 500 mL = 0.5 L, molar mass = 58.44 g/mol, compound = NaCl
- Step 1 — moles
- n = 0.1 × 0.5 = 0.05 mol
- Step 2 — mass
- mass = 0.05 × 58.44 = 2.922 g
- Answer
- Weigh out 2.922 g of NaCl and dilute to 500 mL.
Other chemistry tools
Frequently Asked Questions
What is molarity?
Molarity is the concentration of a solution expressed as moles of solute per litre of solution. A 2 M solution of NaCl contains 2 moles of sodium chloride in every litre of the finished solution. Two details matter for the arithmetic. First, the volume is the volume of the whole solution, not of the solvent you started with — dissolving the solute changes the volume, which is why you make solutions up to the mark in a volumetric flask. Second, the unit symbol M and the unit mol/L mean exactly the same thing, so 0.5 M and 0.5 mol/L are interchangeable in an answer.
What formula does the molarity calculator use?
The base formula is
M = n / V, where M is molarity in mol/L, n is moles of solute, and V is the volume of solution in litres. Rearranged, the same relationship gives n = M × V when you need the moles of solute and V = n / M when you need the volume. Preparing a solution chains one more step, mass = n × molar mass, so the grams you weigh out come from mass = M × V × molar mass. Dilution uses M₁ × V₁ = M₂ × V₂. Each mode prints the formula it used above the substituted numbers, so the working is visible rather than implied.Can I use this calculator for dilution problems?
Yes — dilution is one of the five modes. Choose the dilution tab, fill in any three of M₁, V₁, M₂ and V₂, and leave the box you want empty; the empty field is marked as the unknown and solved from M₁ × V₁ = M₂ × V₂. A worked case: 100 mL of 1.0 M stock diluted to a final volume of 500 mL gives M₂ = (1.0 × 0.100) / 0.500 = 0.20 M. The moles of solute never change during a dilution — only the volume they are spread through does, which is why the two products are equal.
What units should I enter?
Volume accepts litres, millilitres and microlitres; amount accepts moles and millimoles; concentration accepts M, mol/L and mmol/L; molar mass is g/mol and the mass answer comes back in grams with the milligram equivalent next to it. Everything is normalised to litres and moles before the arithmetic, and the conversion line appears in the working — enter 250 mL and you will see "V = 250 mL = 0.25 L" before the division. Values must be greater than zero: a volume or a concentration of zero has no chemical meaning, and dividing by it would not produce an answer, so the calculator says so instead of printing a number.
Is this molarity calculator for homework or lab work?
It is built for studying — checking a homework answer, seeing where a rearrangement went wrong, or revising before an exam. The steps are printed so you can compare them with your own working rather than copy a bare number; an answer without the reasoning is worth little in a chemistry course and nothing on a written exam. For lab work the arithmetic is the same, but real preparation depends on the purity of your reagent, the accuracy of your balance and glassware, and your local safety rules, so treat the result as a calculation to verify rather than a protocol to follow.
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