Quick start
- Enter a formula such as H2O, C6H12O6, or Ca(OH)2.
- Use normal element capitalization.
- Use a period for dot hydrates, such as CuSO4.5H2O.
Best uses
These are the situations this tool is meant for. If your task is close to one of these, the examples and notes below can help you choose the right inputs.
- Find molar mass for common formulas.
- Check element counts in parentheses.
- Estimate mass percentage by element.
- Use the result in the Molarity Calculator.
What this calculator is solving
The Molecular Weight Calculator parses a common chemical formula, counts atoms, multiplies each count by a rounded atomic weight, and adds the parts.
You do not need to memorize the formula first. Start by matching each input label on the calculator to the number, date, unit, or setting you actually have.
The formula in plain language
In plain language: The calculator parses element symbols, subscripts, parentheses, and dot hydrate parts, then adds each element count times its rounded atomic weight. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
If that sounds abstract, use the example cards on the calculator page. They show a complete set of inputs and the kind of answer you should expect.
How to read the answer
Read the headline result first. Then look at the smaller supporting lines because they explain the parts behind the answer, such as totals, units, ranges, or formula steps.
- The main answer is estimated grams per mole.
- Atoms counted tells you whether subscripts and parentheses were read.
- Composition shows the mass share by element.
Common mistakes to avoid
If the answer looks strange, the most likely cause is a small input mismatch: the wrong unit, date, weight, scale, mode, or policy assumption.
- Do not use lowercase-only formulas.
- Do not expect isotope-exact mass from rounded atomic weights.
- Unsupported elements need a reference lookup before they can be calculated.
Research and references
These references shaped the calculator assumptions, unit choices, or safety notes.
Examples from the calculator
About 18.015 g/mol
About 180.156 g/mol
Parentheses parsed
FAQ in plain language
When should I use the Molecular Weight Calculator?
Use it when your task matches one of these common needs: Find molar mass for common formulas. Check element counts in parentheses. It works best when you already know the values, dates, units, or settings the page asks for.
What is the Molecular Weight Calculator doing with my inputs?
In plain language: The calculator parses element symbols, subscripts, parentheses, and dot hydrate parts, then adds each element count times its rounded atomic weight. The examples on the page are there so you can compare your inputs with a filled-out calculation before copying the answer.
What should I double-check before trusting the answer?
The atomic-weight table is rounded and supports common classroom elements. Isotopes, charges, exact masses, and unsupported elements need reference data. Also check that you used the right unit, date, scale, or mode because small input changes can change the result.
Related tools
- Molarity Calculator Calculate molarity from moles and liters or from grams, molar mass, and liters.
- Scientific Calculator A free scientific calculator for trig, logs, roots, powers, and constants.
- Conversion Calculator Convert length, mass, volume, and temperature units with clear formula steps.
Privacy and copying results
Recent answers stay visible only while you work in the current browser tab. They are not sent to a server.
Use Copy answer when you want to paste the expression and result into notes, homework, a message, or another document. Check the units and assumptions before copying.