Toolarithm

Chemistry Calculator

Molar Mass Calculator

Enter a classroom chemical formula to calculate molar mass in grams per mole. The calculator breaks the formula into elements, atom counts, mass contributions, and percent-by-mass rows.

Live calculator

Chemical formula input

Supports common classroom element symbols, parentheses, and hydrates such as CuSO4.5H2O.

Molar mass

74.092 g/mol

Formula

Ca(OH)2

Atoms

5

Elements

3

ElementCountMass% mass
CaCalcium140.07854.09%
HHydrogen22.0162.72%
OOxygen231.99843.19%

Main unit

g/mol

Supports

Parentheses + hydrates

Reference

Atomic weights

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What Can You Create?

Turn formulas into auditable molar-mass rows

Element breakdowns

See each supported element, count, atomic weight, mass contribution, and percent-by-mass share.

Hydrate examples

Check formulas such as CuSO4.5H2O without manually expanding every water molecule first.

Percent composition

Compare how much each element contributes to the compound's total molar mass.

Formula

Molar mass formulas used on this page

Molar mass is the sum of each element count multiplied by its atomic weight. Percent composition compares each element contribution with the total.

Working formulas

Molar mass

M = sum(n_i x atomic weight_i)

Multiply each element count by its atomic weight, then add all contributions.

Mass contribution

element mass = n_i x atomic weight_i

The contribution is shown in grams per mole for each element row.

Percent by mass

percent = element mass / total molar mass x 100

Use this to compare formula composition by mass instead of atom count.

Symbols

M - molar mass
The mass of one mole of formula units, shown in grams per mole.
n_i - element count
The number of atoms of a given element after parentheses and hydrates are expanded.
atomic weight_i - relative atomic weight
The source-backed atomic-weight value used for the element.
percent - percent by mass
The share of total molar mass contributed by one element.
Read the Result

Interpret this calculation before using it

Molar mass is obtained by counting each element in the chemical formula and summing its atomic-weight contribution. Parentheses and subscripts change those counts, so the parsed composition is as important as the final total. The result in grams per mole connects an amount of specified entities with mass for the formula entered.

Worked example

For H2O, two hydrogen atoms and one oxygen atom contribute approximately 2 x 1.008 + 15.999 = 18.015 g/mol using the calculator's tabulated values. For one mole, that is about 18.015 g; for 0.5 mol, multiplying by the same molar mass gives about 9.0075 g before rounding to measurement precision.

Assumptions to keep

  • The formula syntax identifies the intended neutral compound or specified entity and uses correct element capitalization.
  • Atomic-weight values are conventional tabulated values; natural isotopic composition can introduce intervals or sample variation.
  • Hydrates, charges, isotopic labels, mixtures, and empirical formulas require notation the parser explicitly supports.

Limits of this result

A formula calculator does not verify that a compound exists, determine purity, or replace a certificate of analysis. Exact isotope masses differ from standard atomic weights, and practical mass preparation depends on purity and measurement uncertainty. Inspect the element-count table before copying the rounded total.

Useful next step: Dilution Calculator — Use concentration and volume relationships after molar mass has been used to establish the starting amount or solution concentration.

Factual reference:CIAAW standard atomic weights
Why Users Love This Tool

Chemistry results with the formula audit visible

Formula parsing you can check

  • Element rows make it clear which symbols were recognized and how many atoms were counted.
  • Parentheses and hydrate notation are expanded before the mass table is calculated.
  • The percent-by-mass column supports composition questions without a second calculation.
  • Copy and print controls let users keep the parsed result with homework notes.

Source-aware classroom scope

  • The guide links explain that atomic weights are reference values and may be rounded for classroom work.
  • FAQ copy distinguishes molar mass, molecular mass, empirical formulas, and percent composition.
  • Related tools connect molar mass to dilution and pH where concentration units are used.
  • The page avoids medical, dosing, and laboratory safety recommendations; it is an educational calculator.
Perfect For

Molar-mass support for chemistry study

Students

Check formula parsing before using molar mass in stoichiometry or percent-composition practice.

Teachers

Create examples that show each element contribution instead of only the final grams-per-mole value.

Science reviewers

Audit common formulas, hydrates, and rounded atomic-weight assumptions for educational notes.

How It Works

How it works in three quick steps.

1

Enter the formula

Type a formula such as H2O, Ca(OH)2, or CuSO4.5H2O using standard element capitalization.

2

Review element counts

Check the parsed table to confirm each element symbol, atom count, and atomic weight contribution.

3

Use the molar mass

Use the grams-per-mole result for classroom stoichiometry, percent composition, or mole-to-mass checks.

Download & Print

Save or print a molar mass result

Copy the mass summary

Copy the formula, total molar mass, and atom count for notes or classroom answer checks.

Print the formula table

Print the result panel, element table, formulas, FAQ answers, and related chemistry tools.

Compare examples

Switch between common formulas to compare atom count and percent-by-mass changes.

FAQ

Frequently Asked Questions

What does the molar mass calculator support?
The calculator supports common classroom element symbols, whole-number subscripts, parentheses, and hydrate notation written with a dot, such as CuSO4.5H2O. It is designed for educational formulas and transparent checking. If an element is outside the supported set, the page shows a message instead of silently returning a partial result.
How is molar mass different from percent composition?
Molar mass is the total grams per mole for the whole formula. Percent composition divides each element's mass contribution by that total. A compound can have only a few atoms of a heavy element and still have a large mass percentage. Showing both values helps users avoid confusing atom count with mass share.
Why are atomic weights rounded?
Atomic weights are reference values that often include natural isotope abundance ranges. Classroom tables usually round those values to a practical number of decimal places. Toolarithm uses a compact common-element set so the calculation is readable. For high-precision analytical chemistry, users should consult the current reference table required by their course or institution.
Can I use this for empirical formulas and hydrates?
Yes, the calculator can help with empirical-formula practice because it totals the formula exactly as typed. It also handles hydrate notation with a dot, such as CuSO4.5H2O, by counting the waters as part of the total formula. It does not infer a formula from percent data; it calculates the formula the user enters.
Is this calculator for lab safety or medical dosing?
No. This page is an educational chemistry calculator for formula arithmetic and classroom-style checks. Real laboratory preparation, hazardous materials handling, clinical dosing, or quality-control work requires validated procedures, calibrated equipment, and institutional safety review. Use the result as a learning aid, not as a standalone operational instruction.
About This Tool

Why molar mass needs a visible element table

Molar mass is a foundation calculation in chemistry because it connects a written formula with grams per mole. The answer is easy to misuse if the formula was parsed incorrectly. A missing parenthesis, lower-case element error, or hydrate multiplier can change the result before the arithmetic even begins. Toolarithm's Molar Mass Calculator keeps the parsing step visible by showing each element, count, atomic weight, mass contribution, and percent-by-mass share.

The content is intentionally educational. The calculator uses a practical common-element set and rounded atomic weights so students can compare results with classroom reference tables. It links to the concentration guide for users who need to move from grams per mole into molarity, dilutions, or pH relationships. The page avoids lab-safety instructions and medical uses because those contexts require validated procedures beyond a web calculator.

Editorial Transparency

Who maintains this page

Ownership and review

Written and maintained by the Toolarithm editorial team. No review date is shown without a maintained editorial record. No independent professional review is claimed.

Methodology

The method identifies the governing relationship, units, significant assumptions, and educational scope. SI terminology is checked against the BIPM reference.

Read the editorial methodology

Dates and sources

Review dates change only after a substantive method or content check.

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