⚗️

Molecular Weight Calculator

Calculate molecular weight and composition of chemical compounds

Examples: H2O, CO2, C6H12O6, CaCl2, H2SO4

Common Compounds

Molecular Weight Calculator Guide

A molecular weight calculator (molar mass) sums the atomic weights of all atoms in a chemical formula to return mass in g/mol. It supports parentheses, hydrates, and common ions for quick lab prep and homework checks.

What is Molecular Weight Calculator?

The molecular weight calculator parses formulas like C6H12O6 or CuSO4*5H2O, looks up standard atomic weights, multiplies by element counts, and totals them to give molar mass and optional percent composition.

How to Use the Molecular Weight Calculator

  1. Enter a chemical formula (case-sensitive element symbols).
  2. Include parentheses/hydrates as needed (e.g., Ca(OH)2, FeSO4*7H2O).
  3. Calculate molar mass in g/mol and see per-element contributions.
  4. (Optional) view mass percent by element for analytical work.
  5. Copy results for solution prep or reports.

Formulas & Methods

  • Molar mass: M = sum of (n_i * A_i)
    where n_i is count of element i and A_i its atomic weight (g/mol).
  • Mass percent: %_i = (n_i * A_i / M) * 100%
  • Hydrates: treat *xH2O as adding x molecules of water to the formula.

Assumptions & limitations

  • Uses standard atomic weights; isotopic samples differ.
  • Rounding and significant figures should match lab requirements.
  • Does not infer structure or ionization state beyond formula parsing.

Examples

Example A — Water
H2O: M = 2*1.00794 + 15.9994 ~ 18.015 g/mol (values illustrative).

Example B — Glucose
C6H12O6: M ~ 6*12.011 + 12*1.008 + 6*15.999 ~ 180.156 g/mol.

| Compound | Formula | Molar Mass (g/mol, approx) | |---|---|---:| | Water | H2O | 18.015 | | Sodium chloride | NaCl | 58.44 | | Calcium hydroxide | Ca(OH)2 | 74.093 |

Pro Tips & Best Practices

  • Verify capitalization of element symbols (Co vs CO).
  • Match sig figs to your input data or instructor guidelines.
  • For solutions, pair with Stoichiometry and pH tools.

Related Calculators

FAQ

Q: What is molecular weight (molar mass)?

A: The mass of one mole of a substance, expressed in grams per mole (g/mol).

Q: Which atomic weights are used?

A: Standard atomic weights from IUPAC; isotopic composition can cause small variations.

Q: How do I enter a formula?

A: Use element symbols with counts (e.g., C6H12O6). Parentheses and hydrates like CuSO4*5H2O are supported.

Q: Can I calculate mass percent?

A: Yes—mass percent of element = (element mass / total molar mass) * 100%.

Q: What precision should I use?

A: Report g/mol with appropriate significant figures for your data; 2-4 decimals are common.

Engineering note: Units are g/mol. Standard atomic weights assumed; report precision consistently.

Call to Action

Enter a formula and get molar mass and composition instantly—perfect for lab prep, titrations, and homework checks.