Chemistry calculator: molar mass, balancing equations, dilution and pH
Type a chemical formula or an equation and get molar mass with an element breakdown, balanced coefficients, dilution, pH and concentrations in five sections. Equations are balanced exactly, and pH is solved with a quadratic equation, not the textbook shortcut.
Opens without an account 3 times a day. A free account removes the limit.
- 5 sectionsmolar mass, equations, dilution, pH, percent
- Exact fractionsequations balance with no rounding
- 4 kinds of pHstrong and weak acids and bases
- 118 elementsatomic masses by IUPAC 2021
Chemistry calculator: what it calculates
This chemistry calculator is a free online tool from EduFacturing that calculates molar mass from a chemical formula, balances chemical equations, dilutes and prepares solutions, works out the pH of strong and weak acids and bases, and calculates mass percent, volume percent, molarity and molality. The calculation runs in your browser.
What sets it apart from a plain calculator is exactness and warnings. Equations are balanced by a matrix method with exact fractions, not by trial and error. The pH of strong acids and bases is solved with a quadratic equation that holds even in very dilute solutions. A formula with a leading coefficient, such as 2NaCl, is flagged instead of doubling the mass silently.
Molar mass, equations, dilution and pH
Calculates molar mass with a breakdown
It accepts brackets (), [] and {}, nested brackets such as K4[Fe(CN)6] and water of crystallization with "·" or "*", as in CuSO4·5H2O. The table shows element, atom count, atomic mass and contribution.
Balances chemical equations
Type C3H8 + O2 -> CO2 + H2O (an arrow -> or →, or an = sign) and get 1 : 5 : 3 : 4. Before it shows a result, the tool checks that every element balances.
Dilutes and prepares solutions
Pick which of C₁, V₁, C₂, V₂ to solve for and for V₁ or V₂ see how much solvent to add. A separate calculation gives the mass of solid, with the molar mass taken from the formula.
Calculates pH and concentrations
pH for a strong acid, a strong base, a weak acid and a weak base, with Ka or Kb required for the weak ones. The Percentages section gives mass %, volume %, molarity and molality.
When you need a chemistry calculator
A mistake in a chemistry problem is rarely in the multiplication. More often it is a rule applied where it does not hold.
A student with homework
Checks the molar mass of CuSO4·5H2O, balances a combustion equation or checks the pH of 0.01 mol/L hydrochloric acid.
A teacher in class
Shows how brackets and the dot in a hydrate change the mass, and why the moles stay constant in a dilution.
Exam preparation
Checks a hand calculation against the exact result and sees where a unit went wrong, for example mL against L.
How an equation is balanced and pH is solved
Each section is its own calculation with its own checks. Molar mass uses one table of atomic masses, and the input is checked before anything is calculated.
Formula to atoms
The formula is expanded from the innermost bracket outward, and the number before water of crystallization multiplies only that water. A leading coefficient before the whole formula multiplies everything and is flagged.
Matrix for the equation
Each element is a row and each compound a column, with reactants as + and products as −. The null space of the matrix, found by Gaussian elimination over exact fractions, gives the smallest whole-number coefficients.
Charge balance for pH
For a strong acid [H⁺] is solved from [H⁺]² − C·[H⁺] − Kw = 0 with Kw = 10⁻¹⁴, with the water's contribution. For a weak acid, Ka = x² / (C − x) is solved.
| Applies to | Formula | Meaning |
|---|---|---|
| Dilution | C₁·V₁ = C₂·V₂ | the moles of solute do not change; you add V₂ − V₁ of solvent |
| Preparing a solution | m = C·V·M | C in mol/L, V in L, M in g/mol; volume is entered in mL |
| pH of a strong acid | [H⁺] = (C + √(C² + 4·Kw)) / 2 | pH = −log₁₀[H⁺]; Kw = 10⁻¹⁴ at 25 °C |
| pH of a weak acid | [H⁺] = (−Ka + √(Ka² + 4·Ka·C)) / 2 | solution of Ka = x² / (C − x), without the water's contribution |
| Concentrations | molarity = n / V; molality = n / m | n in mol, V of the solution in L, m of the solvent in kg |
What is different from a plain calculator
A matrix instead of trial and error
The fractions are exact, with no rounding, and the result is checked backward: every element has to balance before it is shown.
It does not multiply silently
2NaCl gives 116.88 g/mol, but below the result a note says the formula starts with a coefficient of 2 and that one formula unit weighs 58.44 g/mol.
Formulas do not support ionic charges such as SO4^2-, or fractional subscripts. For unstable elements the mass number of the most stable isotope is used.
pH is at 25 °C. Weak acids and bases are calculated without the water's contribution, and below 1 µmol/L the result is approximate. There is no multistep dissociation: H2SO4 is taken for the first step only.
Questions about molar mass, pH and solutions
How to calculate the molar mass of a hydrate such as CuSO4·5H2O?
Add the atomic masses of the anhydrous salt and of 5 water molecules: 159.602 + 5 · 18.015 = 249.677 g/mol. The dot in the middle is not a decimal point but marks water of crystallization.
How to balance a chemical equation?
With a matrix method over exact fractions, not trial and error: C3H8 + O2 -> CO2 + H2O gives 1 : 5 : 3 : 4. Before it shows a result, the tool checks that every element balances.
How to calculate the pH of a very dilute acid?
Below about 1 µmol/L water itself supplies part of the [H⁺], so the simple −log C is not enough. For 10⁻⁸ mol/L hydrochloric acid the simple formula gives 8 and the exact solution 6.98, so the tool solves the charge balance.
Why does a weak acid need Ka?
How far a weak acid dissociates depends on its Ka, and without it the pH cannot be calculated exactly. For 0.1 mol/L acetic acid with Ka = 1.8 · 10⁻⁵ the pH is 2.88.
What is the difference between molarity and molality?
Molarity is mol per liter of solution and depends on temperature because volume changes. Molality is mol per kg of solvent and does not.
How to make a solution of a given molarity?
Use m = C·V·M, with the volume in liters. For 250 mL of 0.5 mol/L NaCl: 0.5 · 0.25 · 58.44 = 7.305 g of salt.
Is the chemistry calculator free?
Yes. Without an account it opens 3 times a day, and with a free account there is no limit.
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