TOF mass spectrometry calculator

Choose a route, enter the known values and see the rearrangement, unit conversions and answer.

Full TOF equation

t² / d² = m / (2KE)

Enter the atomic or isotopic mass of the ion, M. The calculator converts this into the mass of one ion, m, before using the equation.

Calculate

Your result will appear hereThe calculation will be carried out in SI units and each stage will be shown.

Where the equation comes from: KE = ½mv² and v = d/t. Substituting d/t for v gives KE = md²/(2t²), which rearranges to t²/d² = m/(2KE). Here, m is the mass of one ion in kg, so the calculator uses m = M/(1000L), where L = 6.02214076 × 10²³ mol⁻¹.

Compare two isotopes

t_a / √a = t_b / √b

Calculate

Known mass number, a

Known flight time, tₐ, in seconds

first part × 10 negative power s

Mass number, b

Your result will appear hereThe isotope ratio and substitution will be shown clearly.

Important assumption: the isotope shortcut applies when the ions travel the same distance with the same kinetic energy—equivalently, under the same charge and accelerating conditions. It uses isotope mass numbers as a close approximation to the isotope masses.