Pounds to Kilograms Converter

Formula

kilograms = pounds × 0.45359237

Reverse:

pounds = kilograms × 2.2046226218487757

Formula variables

• pounds — mass in international avoirdupois pounds (lb).
• kilograms — equivalent mass in kilograms (kg).
• 0.45359237 — the exact number of kilograms per pound, fixed by the 1959 international yard and pound agreement.

Worked Examples

Example 1: 1 pound to kilograms

1. Start: 1 lb.
2. Multiply: 1 × 0.45359237 = 0.45359237.
3. Result: 1 pound = 0.45359237 kilograms exactly.

Example 2: 154.32 pounds to kilograms

1. Start: 154.32 lb.
2. Multiply: 154.32 × 0.45359237 = 69.9999... kg.
3. Result: 154.324 lb ≈ 70 kg. This is why 70 kg is often quoted as "about 154 pounds" — the conversion is very close.

Example 3: 200 pounds to kilograms

1. Start: 200 lb.
2. Multiply: 200 × 0.45359237 = 90.718474.
3. Result: 200 pounds = 90.718474 kilograms.

Common Conversion Table

Real-World Uses

• Fitness and body weight: Body weight is measured in kilograms in most countries but in pounds in the US. Weightlifting plates are also labeled differently.
• Shipping and freight: Documentation often requires both metric and imperial weights, especially for international air and sea freight.
• Nutrition and recipes: Ingredient quantities in recipes are sometimes given in pounds but measured in kilograms or grams on international kitchen scales.
• Medicine: Drug dosages are almost universally specified in metric units, and patient weight is often recorded in kilograms internationally — but in pounds in the US.

Unit Definitions

Pound (lb)

The international avoirdupois pound is defined as exactly 0.45359237 kilograms by the 1959 international yard and pound agreement. The word "avoirdupois" distinguishes it from other historical pound definitions such as the troy pound (used for precious metals) and the apothecary pound (obsolete).

Kilogram (kg)

The SI base unit of mass. Since 2019, defined by fixing the Planck constant to exactly 6.62607015 × 10⁻³⁴ J·s. Every mass unit in the SI system ultimately derives from this definition.

Mass vs. Weight

Strictly speaking, kilogram is a unit of mass and pound is also a unit of mass. But in everyday usage, "weight" typically means mass. On Earth's surface, a 70 kg person also weighs about 154 pounds because gravity here is roughly constant. On the Moon, the same person would still have a mass of 70 kg, but the force exerted on the Moon's surface would be about 1/6 as large in newtons. The converter above handles mass conversions only — it does not account for local gravity.

Accuracy and Rounding

Because 1 lb = 0.45359237 kg is exact, any pound value expressible as a finite decimal produces an exact kilogram value in decimal form (subject to floating-point limits). Display precision scales with input magnitude.

Related Converters

• Kilograms to Pounds — the reverse conversion
• Ounces to Grams
• Stones to Kilograms
• All Mass Converters

Frequently Asked Questions