I Built a Free Metal Weight Calculator — Here's the Math Behind It

W = A × L × ρ

// D in mm, returns kg/m
function roundBarWeight(D, density = 7850) {
  const area = (Math.PI / 4) * Math.pow(D / 1000, 2);
  return area * density;
}

// Simplified constant form
function roundBarWeightSimple(D) {
  return (D * D) / 162;
}

// Example: 25mm MS round bar
console.log(roundBarWeightSimple(25)); // 3.858 kg/m

// OD and t in mm, returns kg/m
function pipeWeight(OD, t, density = 7850) {
  const outerArea = (Math.PI / 4) * Math.pow(OD / 1000, 2);
  const innerArea = (Math.PI / 4) * Math.pow((OD - 2 * t) / 1000, 2);
  return (outerArea - innerArea) * density;
}

// Simplified form
function pipeWeightSimple(OD, t) {
  return (OD - t) * t * 0.0246615;
}

// Example: 60.3mm OD, 3.65mm wall (2" IS 1239 medium)
console.log(pipeWeightSimple(60.3, 3.65)); // 5.10 kg/m

// All dimensions in mm, returns kg/m
function hollowSectionWeight(B, H, t, density = 7850) {
  const outerArea = (B / 1000) * (H / 1000);
  const innerArea = ((B - 2 * t) / 1000) * ((H - 2 * t) / 1000);
  return (outerArea - innerArea) * density;
}

// Example: 50×50×3mm SHS (IS 4923)
console.log(hollowSectionWeight(50, 50, 3)); // 4.45 kg/m

// A, B = leg lengths in mm, t = thickness in mm
function angleWeight(A, B, t, density = 7850) {
  const area = ((A + B - t) * t) / 1000000;
  return area * density;
}

// Example: 65×65×6mm equal angle (IS 808)
console.log(angleWeight(65, 65, 6)); // 5.84 kg/m

const DENSITIES = {
  mild_steel:      7850,
  stainless_steel: 8000,
  aluminium:       2700,
  copper:          8960,
  brass:           8500,
  cast_iron:       7200,
  gi:              7850,
  lead:            11340
};

// Divisor = 1,000,000 ÷ (π/4 × density)
function getDivisor(density) {
  return 1000000 / ((Math.PI / 4) * density);
}

console.log(getDivisor(7850));  // 162.3 → MS
console.log(getDivisor(8000));  // 159.2 → SS
console.log(getDivisor(2700));  // 471.5 → Aluminium
console.log(getDivisor(8960));  // 142.5 → Copper