A bit of js that computes the volume of a ConvexHull (or any mesh if you iterate the faces making tetrahedrons with the centerpoint)
import {Vector3} from 'three'
import {ConvexHull} from 'three/examples/jsm/math/ConvexHull.js'
// via https://stackoverflow.com/questions/9866452/calculate-volume-of-any-tetrahedron-given-4-points
function determinant_3x3(m){
return (m[0][0] * (m[1][1] * m[2][2] - m[1][2] * m[2][1]) -
m[1][0] * (m[0][1] * m[2][2] - m[0][2] * m[2][1]) +