Engineering / Browser calculator

Molecular Weight Calculator

Molecular Weight Calculator works from the inputs you provide and returns molar mass (g/mol). Use the calculation panel to explore a scenario, then check the formula and limitations before applying the result.

Your inputs

Your results

Enter your values and calculate to see the result.

Estimates depend on the stated method and entered quantities. Check applicable standards before using a result for a real-world design or safety decision.

Formula and calculation method

Sum each element’s atom count × standard atomic weight. Parentheses multiply grouped atoms.

Standard atomic-weight approximations for common elements. Supports groups, not hydrates, isotope labels, charges or all elements. Unsupported syntax is rejected.

How to use molecular weight calculator

  1. Set Chemical formula (case-sensitive). The example below uses H2O.
  2. Select Calculate to update the result. Reset restores the illustrated inputs. Copy, print or download your own result if you need a record.

Worked example

Example inputs
Chemical formula (case-sensitive)
H2O
Molar mass (g/mol)
18.015

Factors affecting your result

Standard atomic-weight approximations for common elements. Supports groups, not hydrates, isotope labels, charges or all elements. Unsupported syntax is rejected.

Changing chemical formula (case-sensitive) changes the scenario being evaluated. Adjust one input at a time when comparing results, keep a copy of the assumptions, and compare values using the same unit and period. A precise arithmetic result does not make an uncertain assumption precise.

Frequently asked questions

How does the molecular weight calculator work?

Sum each element’s atom count × standard atomic weight. Parentheses multiply grouped atoms.

What inputs does Molecular Weight Calculator need?

Enter chemical formula (case-sensitive). Choose values that correspond to the same situation and measurement convention.

How should I interpret the molecular weight calculator result?

Standard atomic-weight approximations for common elements. Supports groups, not hydrates, isotope labels, charges or all elements. Unsupported syntax is rejected.

Are my molecular weight calculator inputs uploaded?

No. The calculation runs in this browser. Favorites, recent tool names, theme and formatting preferences may be saved locally, but calculation inputs are not sent to a calculation server or stored by this website. Shared links do not include entered values.

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