The formula this page uses
molar mass = Σ (number of atoms × atomic mass) n = m / M M_solution = n / V M₁V₁ = M₂V₂
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Chemistry Calculator
Solve chemistry problems with clear steps, notation, and a final check.
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Calculate without using AI.
Evaluate the governing formula locally in your browser. Define each known quantity once, then change values to test another case instantly.
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Science
Chemistry Calculator explained
The short version
- Molar mass is the mass of one mole, found by adding up the atomic masses in the formula.
- Moles = mass in grams ÷ molar mass. That one line links the balance in your hand to the equation on the page.
- Molarity is moles per litre, so always convert millilitres to litres first.
What each part means
SymbolWhat it means
m — MassIn grams, usually straight off a balance.
M — Molar massIn grams per mole, from the periodic table.
n — AmountIn moles. One mole is 6.022 × 10²³ particles.
V — VolumeIn litres for molarity. 500 mL is 0.5 L.
Show your work: a full example
- The compoundcalcium nitrate, Ca(NO₃)₂
- Count the atoms1 Ca, then the subscript 2 outside the bracket doubles everything inside: 2 N and 6 O
- Calcium1 × 40.08 = 40.08
- Nitrogen2 × 14.01 = 28.02
- Oxygen6 × 16.00 = 96.00
- Add themM = 40.08 + 28.02 + 96.00 = 164.10 g/mol
- Convert a real mass32.82 g ÷ 164.10 g/mol = 0.200 mol
A second, different case
- A different case: make a solution, then dilute itdissolve that 0.200 mol in enough water to make 500 mL
- Convert the volume to litres500 mL = 0.500 L
- Molarity0.200 ÷ 0.500 = 0.400 mol/L, written 0.400 M
- Now take 50 mL of it and dilute to 200 mLM₁V₁ = M₂V₂ with M₁ = 0.400 and V₁ = 50
- Substitute0.400 × 50 = M₂ × 200
- SolveM₂ = 20 ÷ 200 = 0.100 M
- Sanity checkthe volume went up four times, so the concentration went down four times
Copy-ready example
calcium nitrate, Ca(NO₃)₂
The compound
Questions about the Chemistry Calculator
What exactly is a mole?
A counting word, like 'dozen' but far bigger: 6.022 × 10²³ particles. It is chosen so that one mole of a substance weighs its molar mass in grams, which is what makes m ÷ M work at all.
How do I read a formula with brackets?
The subscript outside multiplies everything inside. Ca(NO₃)₂ contains two nitrate groups, so 2 nitrogen atoms and 2 × 3 = 6 oxygen atoms, which is where 96.00 of the 164.10 comes from.
Why do periodic table masses have decimals?
They are weighted averages over the natural isotopes. Chlorine is 35.45 because ordinary chlorine is a mix of about three parts chlorine-35 to one part chlorine-37, not because any single atom weighs 35.45.
What is the difference between molarity and molality?
Molarity is moles per litre of solution and shifts slightly with temperature as liquids expand. Molality is moles per kilogram of solvent and does not, which is why freezing-point and boiling-point problems use molality.