Exact Mass Calculator
Enter a chemical formula and calculate monoisotopic exact mass for mass spectrometry and formula checks.
Quick answer: exact mass uses the most abundant isotope of each element, such as C-12 and H-1, instead of average atomic weight.
Enter a formula to calculate exact mass.
Exact Mass vs Molecular Weight
Exact mass is monoisotopic and is most useful for mass spectrometry. Molecular weight uses standard average atomic weights and is usually better for molarity, percent composition, and solution calculations.