AnyCalc

Utility Tools

Molecular Weight Calculator

Calculate molecular weight from chemical formulas

Reviewed: AnyCalc Editorial|2026-07-19|Editorial policy|About

What this calculator does

The Molecular Weight Calculator computes the molar mass of any chemical compound from its molecular formula. Enter a formula like H2O, NaCl, or C6H12O6 and the tool will calculate the total molecular weight in grams per mole (g/mol). It breaks down the contribution of each element so you can see exactly how the weight adds up. This is essential for chemistry students doing stoichiometry problems, lab professionals preparing solutions, and anyone studying chemical compounds. The calculator recognizes all elements from the periodic table and handles complex formulas with parentheses. It saves time and eliminates manual calculation errors.

How to use

  1. 01
    Enter a chemical formula
    Type a molecular formula like H2O, NaCl, or C6H12O6.
  2. 02
    View the breakdown
    See the atomic weights and element composition of the compound.
  3. 03
    Copy the result
    Copy the calculated molecular weight in g/mol for your work.

Molecular Weight Calculator FAQ

What is the molecular weight of water?▾
The molecular weight of water (H2O) is approximately 18.015 g/mol. This is calculated by adding the atomic masses of two hydrogen atoms (1.008 each) and one oxygen atom (15.999).
What is the difference between molecular weight and molar mass?▾
They are essentially the same value. Molecular weight is typically expressed in atomic mass units (amu), while molar mass is expressed in grams per mole (g/mol). Numerically, they are equal.
How do I enter a chemical formula?▾
Type the formula using element symbols and numbers. For example, type H2O for water, NaCl for table salt, or C6H12O6 for glucose. Use parentheses for groups like Ca(OH)2.

Interpret carefully

Outputs are decision-support estimates, not a substitute for professional judgment.

  • Treating Molecular Weight Calculator output as a final professional diagnosis, quote, or legal determination
  • Entering approximate values when the result is sensitive to units or precision
  • Applying the FAQ answer (“What is the molecular weight of water?”) to a special case without checking assumptions

Next steps

  1. Double-check inputs against your source documents (labs, statements, specs, or notes).
  2. Confirm the method below matches your use case before you act on the number.
  3. For medical, financial, or production decisions, verify with a qualified professional.

Disclaimer: Results are informational only and do not constitute medical, financial, legal, or professional advice. Report issues: sublimernj@gmail.com

← Utility Tools