Weight Converter — kg, lb, Stone, Metric Tonnes & Troy Ounces Explained

Weight is simpler than most unit conversions — but the edge cases matter

Kilograms and pounds dominate everyday weight measurement. Most people know roughly how to convert between them. But the full picture of weight measurement is wider: grams for precise cooking and chemistry, tonnes for heavy cargo and construction, troy ounces for precious metals, stone for body weight in the UK, grains in ballistics and pharmacy. Each context has its preferred unit, and they don't all convert in ways that feel intuitive.

Weight Unit Systems

Metric

• Milligram (mg): Medicine, chemistry — 1mg = 0.001g
• Gram (g): Cooking, postal, precious metals
• Kilogram (kg): Body weight, grocery shopping, everyday reference
• Metric tonne (t): Heavy cargo, construction — 1 tonne = 1,000 kg

Imperial/US Customary

• Ounce (oz): Cooking and postal measurements — 1 oz = 28.35g
• Pound (lb): Body weight in the US, cooking — 1 lb = 453.6g = 16 oz
• Stone (st): Body weight in the UK — 1 stone = 14 lb = 6.35 kg
• US ton (short ton): 2,000 lb = 907.2 kg
• UK ton (long ton): 2,240 lb = 1,016 kg
• Note: The metric tonne (1,000 kg) is also called a "metric ton" and is slightly larger than the US short ton

Specialised

• Troy ounce (ozt): Gold, silver, and precious metals — 1 troy oz = 31.1g (heavier than the regular ounce at 28.35g)
• Grain: Ballistics, pharmacy, gems — 1 grain = 64.8mg

Key Conversions

How to Use the Weight Converter on sadiqbd.com

1. Enter the weight value
2. Select the source unit — mg, g, kg, tonne, oz, lb, stone, troy oz
3. Read the converted values

Real-World Weight Conversions

Body weight tracking

A person weighs 72 kg. In pounds (for US reference) and stone (for UK reference):

72 × 2.205 = 158.8 lb 72 ÷ 6.35 = 11.34 stone = 11 stone 4.7 lb

UK and US health apps often default to different weight units. The converter standardises across all three.

Luggage weight limits

An airline allows 23 kg per checked bag. In pounds:

23 × 2.205 = 50.7 lb (approximately 50 lb)

Many American airlines quote limits in pounds. At check-in, if the scale shows 52 lb:

52 ÷ 2.205 = 23.58 kg — marginally over. Move a 600g (1.3 lb) item to carry-on to comply.

Precious metals investing

Gold is priced in US dollars per troy ounce. At $2,300/troy oz, how much for 50 grams of gold?

50g ÷ 31.1g/troy oz = 1.608 troy oz 1.608 × $2,300 = $3,698

Note the troy ounce (31.1g) vs regular ounce (28.35g) distinction — critical for precious metals calculations. Using the wrong ounce produces a ~10% error.

Cooking: US recipe to metric

Recipe: "2 pounds of chicken breast"

2 × 453.6 = 907.2g ≈ 900g of chicken

Shipping and cargo

A freight shipment weighs 4.5 metric tonnes.

4.5 × 1,000 = 4,500 kg 4,500 × 2.205 = 9,922 lb ≈ 4.96 US short tons

Freight pricing uses different units depending on the carrier (metric tonnes for international shipping, short tons for US domestic freight). The converter keeps the calculations accurate.

The Stone: A Uniquely British Unit

The stone (14 lb = 6.35 kg) is still widely used for body weight in the UK and Ireland, despite being officially deprecated. British people typically describe their weight as "12 stone 3" (12 stone and 3 pounds = 77.6 kg) rather than 77.6 kg or 171 lb.

This creates occasional confusion for healthcare workers and fitness apps designed for international audiences. Converting: take the stones, multiply by 6.35, add pounds multiplied by 0.453 to get kg.

Mass vs. Weight: The Technical Distinction

In physics: mass is the amount of matter in an object (kg); weight is the gravitational force on that mass (newtons). On Earth's surface: weight (N) = mass (kg) × 9.81 m/s².

In everyday life: "weight" and "mass" are used interchangeably. A scale measures gravitational force and displays it as kilograms assuming Earth's gravity. On the Moon, the same scale would show ~⅙ the value because gravity is weaker — but the object's mass (amount of matter) is unchanged.

For all practical purposes outside physics calculations: mass and weight are synonymous, and the weight converter works correctly.

Frequently Asked Questions

Is an ounce the same as a troy ounce? No. Regular ounce (avoirdupois): 28.35g. Troy ounce (precious metals): 31.1g. About 10% heavier. Using regular ounces for gold/silver calculations systematically underestimates by ~10%.

What's the difference between a metric tonne and a US ton? Metric tonne = 1,000 kg = 2,204.6 lb. US short ton = 2,000 lb = 907.2 kg. UK long ton = 2,240 lb = 1,016 kg. Three different "tonnes" — always specify which you mean.

Is the weight converter free? Yes — completely free, no sign-up required.

Weight conversions are essential for health, cooking, travel, and trade. The converter handles everything from milligrams in medication to metric tonnes in shipping — with the critical distinctions (troy vs. regular ounce, metric vs. US ton) handled correctly.

Try the Weight Converter free at sadiqbd.com — convert between mg, g, kg, tonnes, ounces, pounds, stone, and troy ounces instantly.