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Chemistry Tools · Updated October 21, 2026 · Reviewed by FormatFlow Editorial

Mole Calculator

You can convert between mass, moles and particle counts in either direction using molar mass and the Avogadro constant, with each formula and the intermediate values shown in the working.

Runs in your browserFree · No sign-up · No watermark
MASS ↔ MOLESRuns in your browser
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Everything runs locally in this tab. No file is uploaded while the tool loads.

This tool runs in your tab. Nothing is uploaded and no copy is stored.

How files are handled

At a glance

Works with
MASS ↔ MOLES
Processing
In your browser
Price
Free, no account
Updated
October 21, 2026
All Chemistry Tools

About Mole Calculator

The mole is the bridge between the masses measured in a lab and the numbers of atoms and molecules that react. One mole contains exactly 6.02214076 × 10²³ particles, so a mass in grams divided by the molar mass gives moles, and multiplying moles by the Avogadro constant gives a particle count.

This calculator handles all four directions between the three quantities. It shows the formula used, the intermediate value and the result rounded sensibly, with scientific notation for very large particle counts. Molar mass can come from the molar mass calculator on this site if you are starting from a formula.

What this tool does

The details that matter when you use Mole Calculator for real work.

  • Four conversion directions

    Go from mass to moles, moles to mass, moles to particles or particles to moles, with the relevant fields shown for each direction.

  • Exact Avogadro constant

    Particle conversions use the fixed value 6.02214076 × 10²³ per mole rather than a rounded approximation.

  • Scientific notation

    Large particle counts and very small amounts are shown in scientific notation with superscript exponents, so 3.011 × 10²³ stays readable.

  • Step-by-step formulas

    Each result shows n = m / M, m = n × M, N = n × N_A or n = N / N_A with the actual numbers substituted.

  • Sensible range checks

    Empty or non-numeric fields, zero and negative values and fractional particle counts produce clear messages instead of a broken result.

  • Local and private

    All arithmetic runs in the page; the values you type are never uploaded, stored or sent anywhere.

How to use Mole Calculator

No account, no installation — the whole job happens in this browser tab.
  1. 01

    Choose a direction

    Pick mass to moles, moles to mass, moles to particles or particles to moles from the mode buttons.

  2. 02

    Enter the known values

    Type the mass and molar mass, the amount in moles, or the particle count, depending on the mode; scientific notation is accepted for particle counts.

  3. 03

    Read the result

    The headline gives the converted quantity, and the summary grid repeats the mass, moles and particle count where they are known.

  4. 04

    Check the formula

    The working panel substitutes your numbers into the formula, including the Avogadro constant for particle conversions.

  5. 05

    Reset for the next problem

    Press Reset to clear the fields, then switch modes and enter the next set of values.

How this tool works

Works with
MASS ↔ MOLES
Processing
Client-side, in your browser. Nothing is uploaded.
Requirements
Chrome, Edge, Firefox or Safari · JavaScript enabled

Limitations worth knowing

  • Particle counts refer to the entity you have in mind (atoms, molecules or formula units), not automatically to every atom in a formula.
  • Mass conversions use the molar mass you enter; this tool does not parse formulas or look up elements itself.
  • Results are rounded and do not carry an uncertainty estimate for measured masses.

Privacy and file handling

The values you enter are used only for the arithmetic in this browser tab. Nothing is uploaded, stored or logged, and the calculator makes no network request.

Read the full privacy policy

Mole Calculator FAQ

Short, direct answers to the questions people ask before using this tool.
What is a mole?
A mole is the SI unit of amount of substance and contains exactly 6.02214076 × 10²³ elementary entities. That number, the Avogadro constant, links the atomic scale to the gram scale: one mole of carbon-12 atoms has a mass of 12 grams.
How do I convert grams to molecules?
Divide the mass in grams by the molar mass to get moles, then multiply by 6.02214076 × 10²³. For water, 18.015 g is one mole, which is 6.02214076 × 10²³ water molecules.
Are the particles atoms or molecules?
Whichever entity the substance is made of: atoms for a monatomic element such as iron, molecules for a covalent compound such as water, and formula units for an ionic solid such as sodium chloride. The count is per formula unit, so state the entity when you quote a result.
Why is the Avogadro constant 6.02214076 × 10²³?
Since the 2019 SI redefinition the Avogadro constant is fixed exactly at that value, and the mole is defined by it. Earlier values such as 6.022 × 10²³ are rounded versions of the same number.
How precise are the mole conversion results?
The headline result is rounded to four significant figures and the working shows six, with particle counts in scientific notation when they are large. That suits coursework and lab work; high-precision work needs measured molar masses and an uncertainty analysis.
Can I enter an amount in millimoles?
Not directly: enter the value in moles, so 250 mmol becomes 0.25 mol. The calculator expects moles, grams and particles, and the molarity and dilution calculators also work in moles and liters.
Does this tool need the molar mass to count particles?
Only for mass conversions. Moving between moles and particles uses the Avogadro constant alone, so the molar mass field is hidden in those modes.

Background reading

Format guides that explain the trade-offs behind Mole Calculator.