Weight Composition Calculator

Calculate mass percent of a component.

About Weight Composition Calculator

Percent composition for Weight Composition shows how much of a compound's mass each element contributes, which is the basis for empirical formulas. Elements combine in fixed mass ratios, so composition identifies a compound and its formula.

Formula

Weight Composition

Percent composition = element mass / compound mass x 100

composition: The share of each element by mass in a compound

Worked example

With the default values below, Weight Composition Calculator returns Percent Composition of 40.00%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Element massminimum 0 g: 40 g
Compound massminimum 0 g: 100 g
Molar massminimum 0 g/mol: 18 g/mol

Results

Percent Composition: 40.00%
Moles: 5.556 mol
Grams per Mole: 7.20

Step by step

1Values used
2Weight Composition
3Percent Composition= 40.00
4Moles= 5.556 mol
5Grams per Mole= 7.20

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax or fees or charges into account.
Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is Weight Composition calculated?

Percent composition = element mass / compound mass x 100 Percent composition for Weight Composition shows how much of a compound's mass each element contributes, which is the basis for empirical formulas.

Why does Weight Composition matter?

Elements combine in fixed mass ratios, so composition identifies a compound and its formula.

What values do I need to enter?

This calculator takes 3 inputs: Element mass, Compound mass, Molar mass. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.