JSFiddle - React, Tailwind, and code Playground

HTML

<div id="out"></div>

JavaScript

function totalSeconds(time){
    var parts = time.split(':');
    return parts[0] * 3600 + parts[1] * 60 + parts[2];
}

var timeone = "01:23:00"; // time elapsed
var timetwo = "07:34:00"; // total time 
var pct = (100 * totalSeconds(timeone) / totalSeconds(timetwo)).toFixed(2);

document.getElementById("out").innerHTML = pct + '%';