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Pound to Kilogram Converter

Enter a value to see the conversion.

function calculateKg() { var lbValue = document.getElementById('lbInput').value; var resultDisplay = document.getElementById('kgResult'); if (lbValue === "" || isNaN(lbValue)) { resultDisplay.innerHTML = "Please enter a valid number."; return; } var lbs = parseFloat(lbValue); if (lbs < 0) { resultDisplay.innerHTML = "Weight cannot be negative."; return; } // The international avoirdupois pound is equal to exactly 0.45359237 kilograms. var conversionFactor = 0.45359237; var kilograms = lbs * conversionFactor; // Format result: 4 decimal places for accuracy, or fewer if it's a whole number var formattedKg = kilograms % 1 === 0 ? kilograms : kilograms.toFixed(4); resultDisplay.innerHTML = '' + formattedKg + ' kg(' + lbs + ' lb × 0.45359237)'; }

Converting weights from the Imperial system (pounds) to the Metric system (kilograms) is a common requirement in fitness, shipping, aviation, and international trade. While the two units measure the same physical property—mass—they belong to different systems of measurement used globally.

What is a Pound (lb)?

The pound is a unit of mass used primarily in the United States and the United Kingdom (for body weight). The most common type is the international avoirdupois pound, which is legally defined as exactly 0.45359237 kilograms. The abbreviation "lb" comes from the Latin word libra, which refers to scales or a balance.

What is a Kilogram (kg)?

The kilogram is the base unit of mass in the International System of Units (SI). It is used globally for almost all scientific, commercial, and everyday applications outside of the United States. Unlike the pound, which is part of a complex system of ounces and tons, the kilogram is decimal-based, making it easier to scale up to tonnes or down to grams.

The Conversion Formula

To convert pounds to kilograms manually, you use the following mathematical formula:

Weight in Kilograms (kg) = Weight in Pounds (lb) × 0.45359237

For quick mental math, many people use 0.45 as a simplified multiplier, or they divide the pound value by 2.2.

Practical Examples

• Example 1: Body Weight
  If a person weighs 180 lbs, how much is that in kg?
  Calculation: 180 × 0.45359 = 81.646 kg
• Example 2: Shipping
  A package weighs 50 lbs.
  Calculation: 50 × 0.45359 = 22.679 kg
• Example 3: Gym Weights
  A 45 lb barbell plate.
  Calculation: 45 × 0.45359 = 20.411 kg

Pound to Kilogram Conversion Table

Pounds (lb)	Kilograms (kg)
1 lb	0.4536 kg
5 lb	2.2679 kg
10 lb	4.5359 kg
25 lb	11.3398 kg
50 lb	22.6796 kg
100 lb	45.3592 kg
200 lb	90.7184 kg

Why Precise Conversion Matters

In medical settings, dosages are often calculated based on body weight in kilograms. An error in converting pounds to kilograms can lead to incorrect medication administration. Similarly, in the aviation industry, precise weight and balance calculations are critical for safety, where fuel consumption and takeoff speeds are determined by the exact mass of the aircraft and its cargo.