Pounds to Kilograms Converter — Free Weight Tool
Convert pounds to kilograms instantly with our free lbs to kg converter. Perfect for fitness, international travel, and worldwide shipping conversions.
Formula: kilograms = pounds × 0.453592
LBS to KG Conversion Table
| LBS | KG |
|---|---|
| 1 lbs | 0.4536 kg |
| 100 lbs | 45.359 kg |
| 150 lbs | 68.039 kg |
Formula
kilograms = pounds × 0.453592
Example: 1 lbs = 0.4536 kg
Frequently Asked Questions
Looking for the reverse? KG to LBS Converter
About weight conversion
Weight (or more precisely, mass) conversion comes up everywhere from shipping packages and cooking recipes to fitness tracking and pharmacy dosages. The metric system uses grams and kilograms, while the imperial system — still used in the US and UK informally — relies on ounces, pounds, and stones. One kilogram is exactly 2.20462 pounds, a ratio that hasn't changed since the international pound was standardized in 1959. Whether you're converting bodyweight, grocery items, or gold prices, the math uses fixed factors with no regional variation.
How the math works
The kilogram used to be defined by a physical artifact — a platinum-iridium cylinder kept in Paris — but since May 2019 it's defined using Planck's constant, making mass measurement reproducible anywhere on Earth. One pound equals exactly 0.45359237 kilograms. The ounce (16 per pound) is 28.3495 grams. These exact factors are used by customs, airlines, and medical systems worldwide, which is why our converter rounds only at display time.
When you'll use this conversion
- Airline baggage allowances (23 kg limit ≈ 50.7 lbs)
- Cooking and baking recipes from different regions
- Bodyweight tracking for fitness and medical purposes
- International shipping and e-commerce pricing by weight
- Gold, silver, and commodity prices quoted in grams versus ounces
- Medicine dosages, especially for children (mg per kg body weight)
A bit of history
Body-related units like the pound and stone (14 pounds) trace to medieval marketplaces where merchants needed something portable to balance scales. The stone survived in the UK primarily for bodyweight measurement — '12 stone' is still common British usage. The metric kilogram was introduced during the French Revolution and is now the only SI base unit defined by a fundamental physical constant rather than by reference to a specific object.
Common mistakes
- Confusing fluid ounces (volume) with weight ounces — they are completely different
- Assuming 1 kg = 2 lbs for precision work (actual: 2.2046 lbs — a 10% error)
- Using troy ounces (31.1 g, precious metals) when avoirdupois ounces (28.35 g) are needed
- Ignoring the difference between mass (kg) and weight-force (Newtons) in physics
Quick tips
- For mental conversion: 1 kg ≈ 2.2 lbs, 100 g ≈ 3.5 oz, 1 stone ≈ 6.35 kg
- Airline baggage is almost always in kg for international flights — convert before packing
- Gold prices are quoted per troy ounce (31.1035 g), NOT per standard ounce