Chemistry Calculator
Pick a calculation, enter a formula or the numbers you know, and get the answer with the working: molar mass, moles and grams, molarity (M = mol/L) for any unknown, or dilution with C1V1 = C2V2.
Last updated November 4, 2026
Case matters: Co is cobalt, CO is carbon monoxide.
Result
Molar mass of CuSO4·5H2O = 249.677 g/mol
| Molar mass | 249.677 g/mol |
|---|
| Element | Atoms | Atomic weight | Mass (g/mol) | Mass % |
|---|---|---|---|---|
| Cu | 1 | 63.546 | 63.546 | 25.4513% |
| S | 1 | 32.06 | 32.06 | 12.8406% |
| O | 9 | 15.999 | 143.991 | 57.6709% |
| H | 10 | 1.008 | 10.08 | 4.03722% |
Show the work
Formula: molar mass = sum of (atoms of each element × its atomic weight)
- Count the atoms in CuSO4·5H2O: Cu 1, S 1, O 9, H 10.
- Multiply each count by its IUPAC atomic weight: Cu 1 × 63.546 = 63.546; S 1 × 32.06 = 32.06; O 9 × 15.999 = 143.991; H 10 × 1.008 = 10.08.
- Add the parts: 1 × Cu 63.546 + 1 × S 32.06 + 9 × O 15.999 + 10 × H 1.008 = 249.677 g/mol.
- Mass percent of each element = its part ÷ 249.677 × 100: Cu 25.4513%; S 12.8406%; O 57.6709%; H 4.03722%.
Result: Molar mass of CuSO4·5H2O = 249.677 g/mol
The four calculations and their formulas
molar mass = Σ (atoms × atomic weight)
grams = moles × molar mass
M = n ÷ V
C1 × V1 = C2 × V2
Molar mass is the sum of the atomic weights of every atom in the formula. Water, H2O, is 2 × 1.008 + 15.999 = 18.015 g/mol. NaCl is 22.990 + 35.45 = 58.44 g/mol.
Grams equal moles times molar mass, so 0.5 mol of NaCl weighs 29.22 g. Molarity is moles per liter, M = n ÷ V. In a dilution the solute amount stays the same, so C1 × V1 = C2 × V2.
See how we calculate for the formulas, sources and review schedule behind every calculator.
How to type a formula
Use a capital first letter and a lowercase second letter, then the atom count. Case matters: Co is cobalt, CO is carbon and oxygen. Round or square brackets group atoms, as in (NH4)2SO4, and hydrates use a dot, so CuSO4·5H2O counts one Cu, one S, nine O and ten H. Charges and isotopes are not supported.
Atomic weights used
The calculator uses IUPAC 2021 abridged conventional atomic weights for elements 1 to 92 plus Np, Pu, Am and Cm. Radioactive elements with no standard weight, such as technetium and promethium, use the mass number of their longest-lived isotope rather than an IUPAC value. Heavier elements are rejected. Rounding differences can change the last digit.
Sources
Official and primary sources for the statements on this page. Their authors have not reviewed or endorsed this page.
- IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), Standard atomic weights of the elements, abridged values, 2021.. Conventional atomic weights used for every molar mass.
Weights for elements without a standard atomic weight (Tc, Pm, Po, At, Rn, Fr, Ra, Ac, Np, Pu, Am, Cm) are mass numbers of the longest-lived isotope, not IUPAC values.
How to use the Chemistry Calculator
- Choose a calculation: molar mass, moles and grams, molarity or dilution.
- Type the formula, or fill in the values you know and choose which quantity to solve for.
- Read the result, including the element breakdown or the solvent to add.
- Open Show the work to check each substitution, then copy or share the answer.
Worked example
Copper(II) sulfate pentahydrate, CuSO4·5H2O, has a molar mass of 63.546 + 32.06 + 9 × 15.999 + 10 × 1.008 = 249.677 g/mol. Oxygen is 57.67 percent of it, counting nine atoms from the sulfate and the five waters.
| Element | Atoms | Mass (g/mol) | Mass percent |
|---|---|---|---|
| Cu | 1 | 63.546 | 25.45% |
| S | 1 | 32.06 | 12.84% |
| O | 9 | 143.991 | 57.67% |
| H | 10 | 10.08 | 4.04% |
Frequently asked questions
Which atomic weights does the chemistry calculator use?
It uses conventional IUPAC 2021 abridged standard atomic weights, such as H 1.008, C 12.011, O 15.999, Na 22.990 and Cl 35.45. Results can differ slightly from tables that round differently.
Why does the calculator say an element symbol is not supported?
Symbols are case sensitive and must start with a capital letter, so "co" or "CO" is not cobalt. Elements above curium are also not included. Check the capitalisation first, for example Co for cobalt.
Can I convert moles and grams without a formula?
Yes. Leave the formula blank and type the molar mass in g/mol instead. If both are filled in, the formula takes priority and the molar mass box is ignored.
Why does the dilution mode reject some numbers?
Adding solvent can only lower the concentration and raise the volume. If your numbers would make the final concentration higher, or the final volume smaller, you need to evaporate or add solute, which this mode does not model.