Weight Converter
Weight Conversion — Metric, Imperial, and Everything In Between
Weight conversions come up constantly — reading a recipe in grams when you only have a scale in ounces, shipping a package internationally, understanding a drug dosage, or comparing body weight with someone from a different country. This converter handles all the common units instantly so you can get on with what you were doing.
Key Conversion Factors
Real-World Example
The default input is 1 kilogram, which converts to:
- Pounds: 2.205 lbs
- Ounces: 35.27 oz
- Grams: 1,000 g
- Stone: 0.157 st
- Metric tons: 0.001 t
The kilogram-to-pound conversion (×2.205) is the one worth memorizing — it's the most commonly needed in everyday life for people who regularly cross between metric and imperial contexts.
The Metric System — Why Powers of 10 Matter
The metric weight system is built on a single base unit (the gram) with prefixes that represent powers of 10:
- Milligram (mg) = 0.001 g — used for medications and very small quantities
- Gram (g) = base unit — used for food, cooking, postal weights
- Kilogram (kg) = 1,000 g — used for body weight, produce, luggage
- Metric ton (t) = 1,000 kg — used for vehicles, shipping, industrial quantities
Converting within metric is just moving a decimal point. Converting within imperial (ounces → pounds → stone) requires knowing arbitrary conversion factors (16, 14) that don't follow any logical pattern.
The Imperial System — Ounces, Pounds, and Stone
Ounces (oz) are used for small quantities — food portions, beverages, precious metals. Note that "fluid ounces" (volume) are completely different from weight ounces and are often confused.
Pounds (lb) are the primary everyday weight unit in the US — body weight, grocery produce, luggage allowances, shipping.
Stone (st) = 14 pounds. Used almost exclusively in the UK and Ireland for expressing body weight. A person who weighs 70 kg is approximately 11 stone. The unit is rarely used outside these countries but appears regularly in British media and medical contexts.
Practical Weight References
- A standard can of soup: ~400g / ~14 oz / ~0.9 lb
- A bag of sugar: 2 kg / 4.4 lbs
- Average adult human: 70–80 kg / 154–176 lbs / 11–12.5 stone
- A typical car: 1,400–1,800 kg / 1.4–1.8 metric tons / 3,000–4,000 lbs
- A grain of rice: ~25–30 mg
- A standard aspirin tablet: 500 mg / 0.5 g
Frequently Asked Questions
What's the difference between weight and mass?
Technically, mass measures the amount of matter in an object (in kilograms or grams) while weight measures gravitational force on that mass (in newtons). In everyday use, the terms are used interchangeably — your bathroom scale measures weight but displays it in units of mass. On the moon, your mass would be the same but your weight would be about 1/6 of what it is on Earth.
Why are there two types of ounces?
Weight ounces (oz) measure mass: 1 oz = 28.35 grams, 16 oz = 1 pound. Fluid ounces (fl oz) measure volume: 1 fl oz ≈ 29.57 mL (US) or 28.41 mL (UK). They're named similarly but measure completely different things — a fluid ounce of water happens to weigh about 1 weight ounce, but a fluid ounce of honey weighs significantly more.
How do I convert a recipe from cups to grams?
Cups are a volume measurement, not a weight measurement — so the conversion depends entirely on the ingredient's density. 1 cup of water = 240 g, but 1 cup of flour = ~125 g and 1 cup of honey = ~340 g. For baking, weighing ingredients in grams is more accurate than using cups, which is why most professional and international recipes specify grams.
What is a troy ounce?
A troy ounce (used for precious metals like gold and silver) = 31.1035 grams — slightly heavier than a standard avoirdupois ounce (28.35 g). When you see gold prices quoted per ounce, it's always troy ounces. Precious metal weights in this converter use the standard ounce; for gold/silver calculations, note the distinction.
How do I convert kg to lbs in my head?
Multiply kg by 2.2 for a close approximation. 70 kg × 2.2 = 154 lbs (actual: 154.3 lbs). For a more precise mental calculation: multiply by 2 and add 10% of the original. 70 kg × 2 = 140, plus 10% (7) = 147... wait, that gives 147 not 154. The simple "× 2.2" is the easiest shortcut.