Science & Lab

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Molecular Weight Calculator: Chemical Formula Parser

Calculate molecular weight from chemical formula. H2O, Mg(OH)2, CuSO4·5H2O. Live composition breakdown.

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Settings

Decimal Places

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Chemical Formula

Case-sensitive. Subscripts (H2O), parentheses (Mg(OH)2), hydrates (CuSO4·5H2O).

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Common Chemicals

Results

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Enter a chemical formula or pick a common compound

Information Hub

Abridged Standard Atomic Weights (IUPAC 2021)

Click an element symbol to append it to your formula. Weights in g/mol.

Symbol	Name	g/mol
	Hydrogen	1.008
	Helium	4.002602
	Lithium	6.94
	Beryllium	9.0121831
	Boron	10.81
	Carbon	12.011
	Nitrogen	14.007
	Oxygen	15.999
	Fluorine	18.998
	Neon	20.1797
	Sodium	22.98976928
	Magnesium	24.305
	Aluminium	26.9815384
	Silicon	28.085
	Phosphorus	30.973762
	Sulfur	32.06
	Chlorine	35.45
	Argon	39.95
	Potassium	39.0983
	Calcium	40.078
	Scandium	44.955907
	Titanium	47.867
	Vanadium	50.9415
	Chromium	51.9961
	Manganese	54.938043
	Iron	55.845
	Cobalt	58.933194
	Nickel	58.6934
	Copper	63.546
	Zinc	65.38
	Gallium	69.723
	Germanium	72.63
	Arsenic	74.921595
	Selenium	78.971
	Bromine	79.904
	Krypton	83.798
	Rubidium	85.4678
	Strontium	87.62
	Yttrium	88.905838
	Zirconium	91.224
	Niobium	92.90637
	Molybdenum	95.95
	Technetium	97
	Ruthenium	101.07
	Rhodium	102.90549
	Palladium	106.42
	Silver	107.8682
	Cadmium	112.414
	Indium	114.818
	Tin	118.71
	Antimony	121.76
	Tellurium	127.6
	Iodine	126.90447
	Xenon	131.293
	Caesium	132.905452
	Barium	137.327
	Lanthanum	138.90547
	Cerium	140.116
	Praseodymium	140.90766
	Neodymium	144.242
	Promethium	145
	Samarium	150.36
	Europium	151.964
	Gadolinium	157.25
	Terbium	158.925354
	Dysprosium	162.5
	Holmium	164.930329
	Erbium	167.259
	Thulium	168.934219
	Ytterbium	173.045
	Lutetium	174.9668
	Hafnium	178.486
	Tantalum	180.94788
	Tungsten	183.84
	Rhenium	186.207
	Osmium	190.23
	Iridium	192.217
	Platinum	195.084
	Gold	196.96657
	Mercury	200.592
	Thallium	204.38
	Lead	207.2
	Bismuth	208.9804
	Polonium	209
	Astatine	210
	Radon	222
	Francium	223
	Radium	226
	Actinium	227
	Thorium	232.0377
	Protactinium	231.03588
	Uranium	238.02891
	Neptunium	237
	Plutonium	244
	Americium	243
	Curium	247
	Berkelium	247
	Californium	251
	Einsteinium	252
	Fermium	257
	Mendelevium	258
	Nobelium	259
	Lawrencium	262
	Rutherfordium	267
	Dubnium	270
	Seaborgium	269
	Bohrium	270
	Hassium	270
	Meitnerium	278
	Darmstadtium	281
	Roentgenium	281
	Copernicium	285
	Nihonium	286
	Flerovium	289
	Moscovium	289
	Livermorium	293
	Tennessine	293
	Oganesson	294

Formula Blueprint

Parentheses: the multiplier applies to the whole group.

Ca(OH)₂=Ca + 2×(O + H)

→ 1 Ca, 2 O, 2 H

Formula Syntax

Element symbols: Case-sensitive—Na ≠ na
Subscripts: Numbers after symbols (e.g. H2O)
Parentheses: Group with multipliers (e.g. Mg(OH)2)

g/mol vs Da

Molecular weight in g/mol equals the mass in daltons (Da). One mole of molecules has a mass in grams equal to the molecular weight. Labs usually report results in g/mol.

When You Need MW

Molecular weight is used for molarity (M = m / (MW × V)), mass-to-mole conversions, stoichiometry, and preparing solutions of known concentration.

Unicode Subscripts

The parser accepts both C6H12O6 and C₆H₁₂O₆. Unicode subscripts (₀₁₂₃...) are converted automatically.

Molecular Weight from Chemical Formula

Type a formula and see the element breakdown instantly. Each element’s atomic weight (IUPAC 2021) times its count, summed. Use the periodic reference below to click elements into the input.

Core Concepts

The Formula

MW = sum of (atomic weight

\times

count) per element. For glucose

\text{C}_6\text{H}_{12}\text{O}_6

: 6×12.01 + 12×1.01 + 6×16 ≈ 180 g/mol. The Live Audit table shows unit mass and % for each element.

IUPAC Weights

Atomic weights from the 2021 IUPAC table. H 1.008, C 12.011, O 15.999, Fe 55.85. Elements without stable isotopes use the mass number of the longest-lived isotope.

Syntax & Hydrates

Subscripts: H2O, C6H12O6. Groups: Ca(NO3)2 = 1 Ca, 2 N, 6 O. Hydrates: CuSO4·5H2O or CuSO4*5H2O—the dot/star adds the water molecules.

g/mol vs Da

One mole of any compound has a mass in grams equal to its molecular weight. 180 g/mol glucose = 180 Da per molecule. Labs usually report g/mol.

Molecular Weight Calculator: Chemical Formula Parser

Find molecular weight from any formula. H2O, Mg(OH)2, CuSO4·5H2O. Live composition breakdown. IUPAC 2021 weights. No sign-up.

How to Calculate Molecular Weight

Multiply each element’s atomic weight by its count in the formula, then add. Water:

2 \times 1.008 + 15.999 \approx 18.015

g/mol. Glucose:

6 \times 12.011 + 12 \times 1.008 + 6 \times 15.999 \approx 180.16

g/mol. The calculator shows a Live Audit—Element, Count, Unit Mass, and Total Mass %—as you type.

Formula Syntax: Subscripts, Parentheses, Hydrates

Numbers after elements are subscripts: H2O, C6H12O6. Parentheses with a multiplier apply to the whole group: Mg(OH)2 gives 1 Mg, 2 O, 2 H. For hydrates, use a middle dot or asterisk—CuSO4·5H2O or CuSO4*5H2O—so the water molecules add to the main compound. Unicode subscripts (₆, ₁₂) work and are converted automatically.

When You Need Molecular Weight

Molecular weight shows up in molarity (

M = m/(MW \times V)

), stoichiometry, and solution prep. Use this calculator to get MW, then plug it into the Molarity Calculator when you need concentration from mass and volume.

Molecular Weight Calculator FAQ

? How do I find molecular weight from a chemical formula?

Add up (atomic weight × count) for each element. Water

\text{H}_2\text{O}

: 2×1.008 + 15.999 ≈ 18.02 g/mol. Type the formula—NaCl,

\text{H}_2\text{SO}_4

\text{C}_6\text{H}_{12}\text{O}_6

—and the breakdown appears as you type.

? Is molecular weight the same as molar mass?

Same number. Molecular weight is mass per molecule in daltons; molar mass is mass per mole in g/mol. Since 1 Da = 1 g/mol, the values match. Use either term when you need grams per mole.

? Why must element symbols be capitalized correctly?

CO is carbon monoxide; Co is cobalt. First letter uppercase, second lowercase—that’s standard. Wrong case and the parser won’t recognize the element.

? How do I enter hydrates like CuSO4·5H2O?

Use a middle dot (·) or asterisk (*).

\text{CuSO}_4 \cdot 5\text{H}_2\text{O}

is treated as CuSO₄ plus five water molecules. Parentheses work too: Mg(OH)2 means 1 Mg, 2 O, 2 H.

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Science & Lab Reference Note

Educational Use: These tools use standard scientific formulas and accepted constants. Results are intended for learning, homework, and general reference—not for regulated lab work, industrial processes, or clinical applications.

Verification Recommended: Real-world conditions (purity, temperature, pressure, humidity) affect outcomes. For research, manufacturing, or safety-critical work, confirm with a qualified professional or calibrated lab equipment.

Not Professional Advice: This site does not provide chemical, medical, or engineering advice. All calculations run locally in your browser; no data is stored or transmitted.