Weight Converter
Convert between kilograms, pounds and ounces.
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Value
Result
Kilograms:
Pounds:
Ounces:
About Weight Converter
This weight converter converts between metric units (kilograms) and imperial units (pounds, ounces) using precise internationally-defined conversion factors based on the avoirdupois system.
It is useful for shipping calculations, fitness tracking, recipe conversions, international product comparisons, scientific measurements, and any situation requiring conversion between different weight measurement systems.
Conversion Factors Reference
| Unit | Symbol | Kilograms Equivalent | System |
|---|---|---|---|
| Kilogram | kg | 1 (base unit) | Metric (SI) |
| Pound | lb | 0.453592 (exact) | Imperial (Avoirdupois) |
| Ounce | oz | 0.0283495 (exact) | Imperial (Avoirdupois) |
Common Conversion Formulas
Kilograms to Pounds: lbs = kg × 2.20462 Kilograms to Ounces: oz = kg × 35.274 Pounds to Kilograms: kg = lb × 0.453592 Pounds to Ounces: oz = lb × 16 Ounces to Kilograms: kg = oz × 0.0283495 Ounces to Pounds: lb = oz ÷ 16
Metric Weight Prefixes
The metric system uses decimal prefixes for scalable units:
| Unit | Symbol | Grams |
|---|---|---|
| Milligram | mg | 0.001 g |
| Gram | g | 1 g |
| Kilogram | kg | 1,000 g |
| Metric Ton | t | 1,000,000 g |
Imperial Weight Relationships
- 1 pound = 16 ounces - Standard avoirdupois weight
- 1 stone = 14 pounds - Used for body weight in UK/Ireland
- 1 US ton = 2,000 pounds - Short ton, used in US
- 1 UK ton = 2,240 pounds - Long ton, imperial ton
- 1 metric ton = 1,000 kg - Tonne, international standard
Avoirdupois vs Troy Weight
| System | 1 Pound | 1 Ounce | Use Case |
|---|---|---|---|
| Avoirdupois | 453.592 g | 28.3495 g | Everyday weight |
| Troy | 373.242 g | 31.1035 g | Precious metals |
Common Use Cases
- Shipping: Convert package weights for international courier rate calculations
- Fitness: Convert body weight between kg and lbs/stones for travel or competitions
- Cooking: Convert recipe ingredients between metric and imperial measurements
- E-commerce: Display product weights for international customers
- Science: Convert laboratory measurements between unit systems
Accuracy Considerations
The conversion factors used are exact definitions established by international agreement:
- 1 pound is defined as exactly 0.45359237 kilograms (since 1959)
- 1 ounce = 1/16 pound = exactly 0.028349523125 kg
- Results are displayed to 4 decimal places, sufficient for most practical applications
- For precision work (jewelry, pharmaceuticals), use the full factor without rounding
Frequently Asked Questions
- What are the exact conversion factors between weight units?
- The exact conversion factors are: 1 kilogram = 2.20462 pounds = 35.274 ounces. 1 pound = 0.453592 kilograms = 16 ounces. 1 ounce = 0.0283495 kilograms = 0.0625 pounds. These factors are based on the international avoirdupois system.
- What is the difference between mass and weight?
- Mass measures the amount of matter (kilograms, grams) and is constant regardless of location. Weight measures the force of gravity on mass (pounds, newtons) and varies with gravity. On Earth, we use the terms interchangeably since gravity is relatively constant.
- What is the avoirdupois system?
- The avoirdupois system is the standard weight system used in the US and UK for everyday measurements. It defines 1 pound = 16 ounces = 7,000 grains = 0.453592 kg. This differs from troy weight (used for precious metals) where 1 troy pound = 12 troy ounces.
- How do I convert kg to lbs manually?
- To convert kilograms to pounds, multiply by 2.20462. For example: 5 kg × 2.20462 = 11.0231 lbs. To convert pounds to kilograms, divide by 2.20462 (or multiply by 0.453592).
- When should I use metric vs imperial weight units?
- Use metric (kg, g) for scientific work, international shipping, and most countries' daily use. Use imperial (lbs, oz) for US domestic contexts, body weight in the US/UK, and recipes from those regions. Many industries are transitioning to metric.
- What are common weight conversion mistakes?
- Common mistakes include: confusing troy ounces (31.1g) with avoirdupois ounces (28.35g), mixing up kg and lbs in recipes, using approximate factors (2.2 instead of 2.20462) for precision work, and forgetting that 1 stone = 14 lbs (UK body weight).