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Analyze any chemical compound with our free online chemical compound ratio calculator. Enter up to four elements and their masses to get the simplified mass ratio, mole ratio via built-in atomic masses, and step-by-step empirical formula guidance — from water to complex salts.
Analyze CompoundInteractive Chemical Compound Ratio Calculator
Enter at least two elements: the symbol (e.g., H, O, Na, Cl) and its mass in grams. Leave unused rows blank.
Compound Analysis
How the Compound Ratio Calculator Works
From raw masses to mole ratios and empirical formulas in four steps.
Enter Element Symbols
Type each element's symbol — H, O, Na, Cl, Ca, Fe, and 24 more built in. Symbols are matched case-insensitively (h, H, and na all work).
Enter Masses in Grams
Add the mass of each element in your sample. Use at least two elements; rows three and four are optional for ternary and quaternary compounds.
Get Mass and Mole Ratios
The calculator simplifies your mass ratio with the GCD method, converts each mass to moles using standard atomic masses, and simplifies the mole ratio by dividing through by the smallest value.
Read the Empirical Formula
Mole ratios rounded to the nearest whole numbers give the empirical formula — the simplest whole-number ratio of atoms, e.g., H2O from a 2:1 mole ratio of H to O.
Compound Ratio Formulas
Two ratios describe every compound — one you can weigh, one that counts atoms.
Mass Ratio
Example: 2.016 g H and 16.00 g O → GCD ≈ 2.016 → simplified ≈ 1 : 7.94. Mass ratios are directly measurable but do not reveal atom counts.
Moles from Mass
Example: 2.016 g H ÷ 1.008 g/mol = 2.00 mol; 16.00 g O ÷ 15.999 g/mol = 1.00 mol.
Mole Ratio
Divide every mole value by the smallest. For the example: 2.00/1.00 : 1.00/1.00 = 2 : 1 — the true atom ratio.
Empirical Formula
2 : 1 rounds to H2O. When terms land on halves (1 : 1.5), double everything (2 : 3, as in Al2O3 from 1 : 1.5). The calculator flags near-half values.
Mass Percent
Water: H = 2.016/18.015 × 100 = 11.19%, O = 88.81%.
Built-in Atomic Masses
The calculator recognizes these 30 common elements by symbol (standard atomic weights, g/mol).
| Symbol | Element | Atomic Mass | Symbol | Element | Atomic Mass |
|---|---|---|---|---|---|
| H | Hydrogen | 1.008 | P | Phosphorus | 30.974 |
| He | Helium | 4.003 | S | Sulfur | 32.06 |
| Li | Lithium | 6.94 | Cl | Chlorine | 35.45 |
| Be | Beryllium | 9.012 | Ar | Argon | 39.948 |
| B | Boron | 10.81 | K | Potassium | 39.098 |
| C | Carbon | 12.011 | Ca | Calcium | 40.078 |
| N | Nitrogen | 14.007 | Fe | Iron | 55.845 |
| O | Oxygen | 15.999 | Cu | Copper | 63.546 |
| F | Fluorine | 18.998 | Zn | Zinc | 65.38 |
| Ne | Neon | 20.180 | Br | Bromine | 79.904 |
| Na | Sodium | 22.990 | Ag | Silver | 107.87 |
| Mg | Magnesium | 24.305 | I | Iodine | 126.90 |
| Al | Aluminium | 26.982 | Au | Gold | 196.97 |
| Si | Silicon | 28.085 | Pb | Lead | 207.2 |
| Need another element? Enter its symbol — if unrecognized, the calculator will ask for its atomic mass is not supported; use the 30 built-in elements. | |||||
Famous Compounds and Their Ratios
Test the calculator against these classics — enter the masses and confirm the formula.
| Compound | Masses In | Mole Ratio | Formula |
|---|---|---|---|
| Water | 2.016 g H, 16.00 g O | 2 : 1 | H2O |
| Carbon dioxide | 12.011 g C, 32.00 g O | 1 : 2 | CO2 |
| Table salt | 22.99 g Na, 35.45 g Cl | 1 : 1 | NaCl |
| Glucose | 72.07 g C, 12.10 g H, 96.00 g O | 6 : 12 : 6 → 1:2:1 | C6H12O6 (empirical CH2O) |
| Alumina | 53.96 g Al, 48.00 g O | 2 : 3 | Al2O3 |
Why Mole Ratio Beats Mass Ratio
Mass ratios are what you measure; mole ratios are what chemistry obeys. Reactions balance in moles, not grams — 2 g of H2 reacts with 16 g of O2 because that is 2 mol : 1 mol, even though the mass ratio looks lopsided at 1:8. Always convert to moles before reasoning about formulas or stoichiometry.
Deeper reading: empirical formula and stoichiometry on Wikipedia.
From Mole Ratios to Balanced Equations
The mole ratio is the bridge between composition analysis and reaction stoichiometry — the same numbers that give you a formula also balance your equations.
Reading a Balanced Equation as a Ratio
2H2 + O2 → 2H2O encodes the mole ratio 2:1:2. Need 4 mol of water? Double everything: 4 mol H2 + 2 mol O2. The coefficients are a mole ratio, which is why this calculator's output plugs straight into stoichiometry problems.
Limiting Reactant via Ratios
Given 5 mol H2 and 2 mol O2 for the reaction above: the equation demands H2:O2 = 2:1, but you have 5:2 = 2.5:1 — hydrogen is in excess, oxygen limits. Divide each available amount by its coefficient (5/2 = 2.5, 2/1 = 2); the smallest quotient identifies the limiter.
Percent Yield Uses the Same Math
Theoretical yield comes from the mole ratio; percent yield = (actual ÷ theoretical) × 100. A synthesis giving 8.5 g of product against a 10.0 g theoretical yield is an 85% yield — the ratio habit again.
Combustion Analysis: Ratios in Reverse
Burn an unknown hydrocarbon, weigh the CO2 and H2O produced, and back-calculate the C:H mole ratio of the fuel. Every carbon becomes one CO2; every two hydrogens become one H2O. It is the empirical-formula workflow run backwards, and refineries use it daily.
Chemical Compound Ratio FAQs
Mass ratio compares grams (what you weigh); mole ratio compares numbers of atoms (what reacts). Convert mass to moles with n = m ÷ atomic mass, then divide by the smallest. Water's mass ratio H:O is about 1:8, but its mole ratio — the chemically meaningful one — is 2:1.
Assume 100 g: percents become grams. Enter those masses here. Convert to moles, divide by the smallest, round to integers. Example: 40.0% C, 6.7% H, 53.3% O → 3.33, 6.65, 3.33 mol → 1:2:1 → CH2O.
It normalizes the ratio so the least abundant element becomes 1, revealing the simplest whole-number relationship. It is the same as simplifying a fraction — 4:2 becomes 2:1.
Multiply everything to clear the fraction: 1:1.5 → 2:3 (as in Al2O3). Common multipliers: ×2 clears halves, ×3 clears thirds, ×4 clears quarters. The calculator flags values within 0.05 of a half.
Empirical is the simplest ratio (CH2O); molecular is the actual atom count (C6H12O6 for glucose). Divide the measured molar mass by the empirical formula mass and multiply the subscripts by that integer.
30 common elements from H to Pb, matched case-insensitively by symbol (type "na" or "Na" for sodium). Symbols follow the standard one-uppercase-then-lowercase convention — "CL" will not match, "Cl" will.
Yes — treat the water as H and O entries alongside Cu, S, O. For CuSO4·5H2O enter Cu: 63.55 g, S: 32.06 g, O (total): 144 g, H: 10.08 g. The mole ratio 1:1:9:10 reveals the waters of crystallization.
Charge balance. Na+ and Cl− are singly charged, so one of each neutralizes (NaCl). Oxygen needs two electrons (O2−), so it takes two H+ ions (H2O). Mole ratios encode this ionic logic directly.
Worked Example: Finding Alumina's Formula
A sample contains 53.96 g aluminium and 48.00 g oxygen. What is the empirical formula?
Step 1: Moles — Al: 53.96 ÷ 26.982 = 2.00 mol; O: 48.00 ÷ 15.999 = 3.00 mol.
Step 2: Divide by smallest — 2.00/2.00 : 3.00/2.00 = 1 : 1.5.
Step 3: Clear the half — ×2 → Al2O3.
Step 4: Check — formula mass = 2(26.982) + 3(15.999) = 101.96 g/mol ✓.