Weight Converter - Free Online Tool

Last updated March 22, 2026

Weight Converter — Examples

The Weight Converter converts between all major weight and mass units instantly. Here are practical examples for common conversion scenarios.

Common Conversions

// JavaScript — weight conversion utility
const CONVERSIONS_TO_KG = {
  kg:        1,
  g:         0.001,
  mg:        0.000001,
  lb:        0.453592,
  oz:        0.0283495,
  stone:     6.35029,
  metric_ton: 1000,
  short_ton: 907.185,
  long_ton:  1016.05,
  carat:     0.0002,
  troy_oz:   0.0311035
};

function convert(value, fromUnit, toUnit) {
  const kg = value * CONVERSIONS_TO_KG[fromUnit];
  return kg / CONVERSIONS_TO_KG[toUnit];
}

// Examples
console.log(convert(1, "kg", "lb").toFixed(4));    // 2.2046 lbs
console.log(convert(1, "lb", "kg").toFixed(4));    // 0.4536 kg
console.log(convert(100, "g", "oz").toFixed(4));   // 3.5274 oz
console.log(convert(1, "stone", "kg").toFixed(4)); // 6.3503 kg

# Python — weight conversion
CONVERSIONS_TO_KG = {
    "kg":         1,
    "g":          0.001,
    "mg":         0.000001,
    "lb":         0.453592,
    "oz":         0.0283495,
    "stone":      6.35029,
    "metric_ton": 1000,
    "short_ton":  907.185,
    "troy_oz":    0.0311035,
    "carat":      0.0002,
}

def convert(value, from_unit, to_unit):
    kg = value * CONVERSIONS_TO_KG[from_unit]
    return kg / CONVERSIONS_TO_KG[to_unit]

# Examples
print(f"1 kg = {convert(1, 'kg', 'lb'):.4f} lb")
print(f"1 lb = {convert(1, 'lb', 'kg'):.4f} kg")
print(f"100 g = {convert(100, 'g', 'oz'):.4f} oz")
print(f"1 stone = {convert(1, 'stone', 'kg'):.4f} kg")

Kilograms to Pounds and Ounces

// Convert kg to pounds and ounces (mixed format)
function kgToLbOz(kg) {
  const totalOz = kg * 35.274;
  const lb = Math.floor(totalOz / 16);
  const oz = (totalOz % 16).toFixed(2);
  return { lb, oz, display: `${lb} lb ${oz} oz` };
}

console.log(kgToLbOz(1));    // 2 lb 3.27 oz
console.log(kgToLbOz(5));    // 11 lb 0.37 oz
console.log(kgToLbOz(0.5));  // 1 lb 1.64 oz

Stone and Pounds (UK Body Weight)

// Convert kg to stone and pounds (UK format)
function kgToStoneLb(kg) {
  const totalLb = kg * 2.20462;
  const stone = Math.floor(totalLb / 14);
  const lb = (totalLb % 14).toFixed(1);
  return { stone, lb, display: `${stone} st ${lb} lb` };
}

// Convert stone and pounds to kg
function stoneLbToKg(stone, lb) {
  return (stone * 14 + lb) * 0.453592;
}

console.log(kgToStoneLb(70));   // 11 st 0.2 lb
console.log(kgToStoneLb(80));   // 12 st 8.4 lb
console.log(stoneLbToKg(11, 0).toFixed(2)); // 69.85 kg

Cooking Conversions

# Python — cooking weight conversions
def cooking_conversions(grams):
    """Convert grams to common cooking units."""
    return {
        "grams": grams,
        "kg": grams / 1000,
        "oz": grams / 28.3495,
        "lb": grams / 453.592,
        "tsp_approx": grams / 4.2,   # approximate for water-density ingredients
        "tbsp_approx": grams / 12.6  # approximate
    }

# Common ingredient weights
ingredients = {
    "1 cup flour": 120,
    "1 cup sugar": 200,
    "1 cup butter": 227,
    "1 tbsp olive oil": 14,
}

for ingredient, grams in ingredients.items():
    result = cooking_conversions(grams)
    print(f"{ingredient}: {grams}g = {result['oz']:.2f}oz = {result['lb']:.3f}lb")

Precious Metals (Troy Ounces)

// Troy ounce conversions for precious metals
const TROY_OZ_TO_GRAMS = 31.1035;

function troyOzToGrams(troyOz) {
  return troyOz * TROY_OZ_TO_GRAMS;
}

function gramsToTroyOz(grams) {
  return grams / TROY_OZ_TO_GRAMS;
}

// Note: 1 troy oz ≠ 1 regular oz
// 1 troy oz = 31.1035 g
// 1 regular oz = 28.3495 g

console.log(`1 troy oz = ${TROY_OZ_TO_GRAMS} grams`);
console.log(`100g gold = ${gramsToTroyOz(100).toFixed(4)} troy oz`);

Shipping Weight Calculations

# Python — shipping weight conversion for international orders
def shipping_weight(weight_kg):
    """
    Convert weight for international shipping labels.
    US carriers use pounds, international use kg.
    """
    return {
        "kg": round(weight_kg, 3),
        "g": round(weight_kg * 1000, 1),
        "lb": round(weight_kg * 2.20462, 3),
        "oz": round(weight_kg * 35.274, 2),
        "display_us": f"{weight_kg * 2.20462:.2f} lb",
        "display_metric": f"{weight_kg:.3f} kg"
    }

# Example: product weights
products = [
    ("Laptop", 1.8),
    ("Phone", 0.174),
    ("Book", 0.45),
]

for name, kg in products:
    w = shipping_weight(kg)
    print(f"{name}: {w['display_metric']} / {w['display_us']}")

Unit Reference

• 1 kilogram (kg) = 1,000 grams = 2.20462 pounds
• 1 pound (lb) = 16 ounces = 0.453592 kg
• 1 stone = 14 pounds = 6.35029 kg
• 1 metric ton = 1,000 kg = 2,204.62 pounds
• 1 troy ounce = 31.1035 grams (used for precious metals)
• 1 carat = 0.2 grams (used for gemstones)

The Weight Converter handles all these units and more, with precision suitable for scientific, commercial, and everyday use.