Relative formula mass and moles calculator

Type a formula to see its relative formula mass (M_r) with every step of the working, then use it to find moles. Check your own working against it, not the other way round.

Relative formula mass

Formula, for example H2O, CaCO3, Ca(OH)2 or (NH4)2SO4

Moles

moles = mass (g) ÷ M_r. Mass = moles × M_r.

Mass in g or moles

Higher tier content in GCSE Chemistry. Answers are given to 3 significant figures.

Practice: work out M_r

Ten formulae to work out on paper. Type your answer to check it.

Relative atomic masses used

Relative atomic masses as printed on the AQA GCSE periodic table, which rounds all values except Cl (35.5) and Cu (63.5). Elements shown in square brackets on that table (mass numbers of the longest-lived isotope) are left out. Always use the periodic table given in your own exam.

Show the table

Symbol	Element	A_r
H	Hydrogen	1
He	Helium	4
Li	Lithium	7
Be	Beryllium	9
B	Boron	11
C	Carbon	12
N	Nitrogen	14
O	Oxygen	16
F	Fluorine	19
Ne	Neon	20
Na	Sodium	23
Mg	Magnesium	24
Al	Aluminium	27
Si	Silicon	28
P	Phosphorus	31
S	Sulfur	32
Cl	Chlorine	35.5
Ar	Argon	40
K	Potassium	39
Ca	Calcium	40
Sc	Scandium	45
Ti	Titanium	48
V	Vanadium	51
Cr	Chromium	52
Mn	Manganese	55
Fe	Iron	56
Co	Cobalt	59
Ni	Nickel	59
Cu	Copper	63.5
Zn	Zinc	65
Ga	Gallium	70
Ge	Germanium	73
As	Arsenic	75
Se	Selenium	79
Br	Bromine	80
Kr	Krypton	84
Rb	Rubidium	85
Sr	Strontium	88
Y	Yttrium	89
Zr	Zirconium	91
Nb	Niobium	93
Mo	Molybdenum	96
Ru	Ruthenium	101
Rh	Rhodium	103
Pd	Palladium	106
Ag	Silver	108
Cd	Cadmium	112
In	Indium	115
Sn	Tin	119
Sb	Antimony	122
Te	Tellurium	128
I	Iodine	127
Xe	Xenon	131
Cs	Caesium	133
Ba	Barium	137
La	Lanthanum	139
Hf	Hafnium	178
Ta	Tantalum	181
W	Tungsten	184
Re	Rhenium	186
Os	Osmium	190
Ir	Iridium	192
Pt	Platinum	195
Au	Gold	197
Hg	Mercury	201
Tl	Thallium	204
Pb	Lead	207
Bi	Bismuth	209

Sources

AQA GCSE Chemistry and Combined Science periodic table (8462/8464/8465 insert, June 2018)

Relative formula mass and moles calculator