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Molkit

Formula & Molecular Weight

Molkit shows the molecular formula and molecular weight of the current selection in the status bar. Select atoms, read the result, click to copy. The readout updates live as you edit.

Where it appears

The readout sits in the status bar at the bottom of the window. It shows the formula in Hill order (carbon first, then hydrogen, then the remaining elements alphabetically) with proper subscripts, followed by the average molecular weight to two decimal places, for example C6H6 MW: 78.11.

Selection scope

The readout is selection-scoped. It appears only while atoms are selected and clears when nothing is selected; there is no whole-canvas fallback. To get the formula for everything on the canvas, press Ctrl+A to select all first.

If your selection spans more than one molecule, the readout sums every selected atom into a single combined formula and weight. To read one molecule at a time, select just that molecule.

Copy to clipboard

Click the readout to copy the formula and weight as plain text (for example C6H6 MW: 78.11). The readout flashes briefly to confirm the copy. The same action is available as View > Copy Formula to Clipboard and in the command palette.

Hiding the readout

View > Show Formula & Weight toggles the readout on and off. A check mark next to the menu item shows the current state. The command palette lists it as “Toggle Formula & Weight”.

What counts toward the formula

  • Implicit hydrogens are included, using the same count the canvas draws on atom labels. The count comes from standard valences for C, N, O, S, P, B, F, Cl, Br, I, and H; other elements contribute no implicit hydrogens.
  • Charges adjust the implicit hydrogen count through the valence rule, so a protonated or deprotonated atom changes the hydrogen total. The charge itself is not appended to the formula text.
  • Explicit lone pairs switch an atom to full octet accounting, which can change its implicit hydrogen count.
  • Collapsed abbreviations are not expanded. A collapsed group such as OMe counts only its visible attachment atom, so expand abbreviations before reading the formula if you need the complete composition.

See also