Molecular Weight Calculator
Calculate molecular weight from chemical formulas with element-by-element breakdown
Use element symbols (e.g., H, C, O, Na, Cl). Numbers indicate atom counts. Parentheses are supported.
How to Use
Basic Formulas
Enter element symbols followed by numbers: H2O, CO2, NaCl
Parentheses
Use parentheses for groups: Ca(OH)2, (NH4)2SO4
Element Symbols
First letter uppercase, second lowercase: Na, Mg, Fe, Au
Common Elements
H
1.01
He
4.00
Li
6.94
Be
9.01
B
10.81
C
12.01
N
14.01
O
16.00
F
19.00
Ne
20.18
Na
22.99
Mg
24.30
Al
26.98
Si
28.09
P
30.97
S
32.06
Click to add element to formula
Find Element
H
Hydrogen
1.01
He
Helium
4.00
Li
Lithium
6.94
Be
Beryllium
9.01
B
Boron
10.81
C
Carbon
12.01
N
Nitrogen
14.01
O
Oxygen
16.00
F
Fluorine
19.00
Ne
Neon
20.18
Na
Sodium
22.99
Mg
Magnesium
24.30
Al
Aluminum
26.98
Si
Silicon
28.09
P
Phosphorus
30.97
S
Sulfur
32.06
Cl
Chlorine
35.45
Ar
Argon
39.95
K
Potassium
39.10
Ca
Calcium
40.08
Sc
Scandium
44.96
Ti
Titanium
47.87
V
Vanadium
50.94
Cr
Chromium
52.00
Mn
Manganese
54.94
Fe
Iron
55.84
Co
Cobalt
58.93
Ni
Nickel
58.69
Cu
Copper
63.55
Zn
Zinc
65.38
Quick Reference
MW Calculation
MW = Σ(atomic weight × atom count)
Molar Mass
Mass of 1 mole in grams = MW in g/mol
% Composition
(Element mass / Total mass) × 100%
About Molecular Weight
What is Molecular Weight?
Molecular weight (MW) is the sum of atomic weights of all atoms in a molecule. It's expressed in atomic mass units (amu) or grams per mole (g/mol).
Applications
- • Stoichiometric calculations
- • Solution preparation (molarity)
- • Analytical chemistry
- • Pharmaceutical formulations
Limitations
- • Isotopic variations not considered
- • Average atomic weights used
- • Hydrates require separate calculation
- • Ionic compounds show formula weight