- What is molar mass?
- Molar mass is the mass of one mole (6.022 × 10²³ particles) of a substance, expressed in grams per mole (g/mol). For an element it's just the atomic weight from the periodic table (carbon = 12.011 g/mol). For a compound it's the sum of the atomic weights of every atom in the formula. One mole of water (H2O) has a mass of 18.015 g; one mole of glucose (C6H12O6) is 180.156 g.
- How do I write a formula the calculator can read?
- Element symbols use a capital letter optionally followed by one lowercase letter — Na (sodium), Cl (chlorine), Fe (iron). Subscripts are plain digits right after the symbol or after a closing paren: H2O, Ca(OH)2, Mg3(PO4)2. Don't lowercase the first letter (na is wrong; Na is right). Real Unicode subscripts (H₂O, C₆H₁₂O₆) work too — paste them in and the calculator converts them.
- Does it handle parentheses?
- Yes, including nested ones. Ca(OH)2 means one calcium plus two hydroxide groups (so two oxygens and two hydrogens). Mg3(PO4)2 means three magnesiums plus two phosphate groups (so two phosphorus and eight oxygens). (NH4)2SO4 (ammonium sulfate) puts two ammonium groups in front of a sulfate — the calculator multiplies the inside of each pair of parens by whatever number follows the closing paren.
- What about hydrates with the dot — like CuSO4·5H2O?
- Supported. Use a center dot (·), a bullet (•), or a plain period (.) between the anhydrous part and the water-of-crystallization. The number after the dot multiplies everything that follows. CuSO4·5H2O = 159.602 (CuSO4) + 5 × 18.015 (water) = 249.677 g/mol — the textbook value for blue vitriol.
- Which atomic weights are you using?
- IUPAC 2021 standard atomic weights, abridged to 3–4 decimal places (the same precision used in undergraduate chemistry textbooks). For elements with no stable isotope (Tc, Pm, Po, At, Rn, Fr, Ra, and the actinides and transactinides past uranium) the table uses the mass number of the most-stable isotope, in line with the IUPAC convention. All 118 elements are in the table.
- Why isn't NaCl exactly 58.5?
- Because the atomic weights aren't whole numbers. Sodium is 22.990 and chlorine is 35.453, so NaCl = 58.443 g/mol. The 58.44 you see in most textbooks is the same number rounded one place earlier. Both are correct — the calculator shows three decimals because that's what most stoichiometry problems require.
- What does the per-element breakdown tell me?
- Each row shows the element symbol, how many atoms of it appear in the formula, the atomic weight (g/mol), and the subtotal (count × atomic weight). The rows are ordered by the Hill system — carbon first, hydrogen second, the rest alphabetical — the same convention CAS and most journals use. The breakdown is the working-out chemistry teachers ask for on a stoichiometry problem.
- Can I use this to find moles from grams?
- Indirectly — divide your mass in grams by the molar mass this tool gives you, and you have the amount in moles. For that one-step conversion in a single view, use the Grams to Moles converter (linked below) — same chemistry, plus a built-in compound picker.
- Is my data saved anywhere?
- No. The math runs entirely in your browser. No servers, no logs, no accounts.
