Weight Converter: what this tool is for
Accurate weight and mass conversion is indispensable across everyday life, fitness tracking, culinary baking, laboratory dosing, and international freight logistics: measuring baking ingredients from American recipes in ounces (oz) and pounds (lb), converting body weight on British scales in stones (st), or calculating air cargo allowances in kilograms and pounds. Xorvian's Weight & Mass Converter delivers instant, high-precision conversions across all standard international mass units.
The tool supports 7 standardized units across both the metric International System and the imperial / US customary systems: Milligrams (mg), Grams (g), Kilograms (kg, the fundamental SI base unit), Metric Tons (t), Avoirdupois Ounces (oz), Avoirdupois Pounds (lb), and British Stones (st).
Mass measures the intrinsic quantity of matter in an object, while weight is the gravitational force exerted on that mass. In terrestrial civil and commercial contexts, these concepts share identical linear conversion ratios relative to the kilogram. The calculation applies exact metrological factors with complete mathematical symmetry.
Frequent mass conversion mistakes include confusing commercial avoirdupois ounces (28.35 g) with precious-metal troy ounces (31.10 g), mixing up fluid ounces (volume) with weight ounces (mass), or forgetting that a British stone contains exactly 14 pounds rather than 10.
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Nothing is saved on our servers, during or after processing.
Local processing
The computation runs in your browser whenever the technology allows it.
Instant result
No waiting and no export queue: the result appears live.
Free, no account
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What this tool gives you
7 Standard Metric & Imperial Units
Convert seamlessly between milligrams, grams, kilograms, metric tonnes, ounces, pounds, and British stones.
Legally Standardized Exact Factors
Built on international treaty definitions: 1 avoirdupois pound = 453.59237 g exact and 1 avoirdupois ounce = 28.349523125 g exact.
Simultaneous Multi-Unit Matrix
Inspect your converted mass across all 6 other units at once in a clear side-by-side comparative table.
Tailored for Baking, Fitness & Freight
Instantly translate US recipes, gym progress logs, or international air freight customs declarations.
Instant One-Click Swap
Reverse source and target units immediately with the bidirectional swap button without retyping numbers.
Flexible Comma & Decimal Point Support
Parses both periods and commas smoothly for fast input on desktop keyboards and mobile number pads.
Real-world examples
Official mathematical conversion factors relative to the kilogram and common real-world mass benchmarks:
Adapting American Baking Recipes
A brownie recipe calls for 8 oz of dark chocolate and 0.75 lb of caster sugar. Converting to grams gives 226.8 g of chocolate and 340.2 g of sugar, making it straightforward to measure on a standard kitchen digital scale.
International Freight and Customs Declarations
An e-commerce seller in Europe ships a parcel weighing 2.4 kg to a US customer. Converting 2.4 kg to pounds gives 5.29 lbs, which is entered directly onto the carrier's international shipping label.
Body Weight Tracking in the United Kingdom
A traveler stepping on a bathroom scale in London reads 12 stone 4 lbs (172 lbs total). Converting this figure to kilograms gives 78.02 kg, enabling consistent fitness tracking against European medical metrics.
Pharmaceutical Formulation in Milligrams
A compounding pharmacist needs to convert an active ingredient dosage of 250 mg into grams for batch recording. The converter provides 0.25 g with complete precision.
How to use Weight Converter
Enter the Mass Value
Type your number into the 'Value' field. Both decimals with periods (2.5) and commas (2,5) are supported.
Choose the Source Unit
Select the unit your initial weight is measured in (e.g., Pounds lb) from the starting selector.
Choose the Target Unit
Select the unit you want your result in (e.g., Kilograms kg) from the target selector.
Swap Units with One Click
Click the bidirectional arrow button to instantly reverse source and target units.
Copy the Result
Click the copy button to copy the formatted converted weight directly to your clipboard.
Review the Multi-Unit Comparison
Check the multi-unit table below the result to see your weight converted across all other 6 mass units simultaneously.
Tips and mistakes to avoid
Mental Kitchen Math Rules of Thumb
Remember that 1 ounce is approximately 28.35 grams, and 1 pound is about 454 grams (slightly less than half a kilogram).
Convert British Stones and Pounds
To convert 11 st 7 lb to kilograms, convert stones to total pounds first: (11 × 14) + 7 = 161 lbs. Then multiply by 0.45359237 to get 73.03 kg.
Understand the 23 kg vs. 50 lb Airline Standard
International airlines set standard checked luggage at 23 kg in metric countries and 50 lbs in the US. 50 lbs is exactly 22.68 kg, giving metric travelers a slight 320-gram safety buffer.
Volume vs. Mass Distinction in Liquids
1 liter of water weighs 1 kg, but 1 liter of olive oil weighs roughly 0.92 kg and 1 liter of honey weighs about 1.42 kg. Do not interchange weight ounces (oz) with fluid ounces (fl oz).
Avoid : Confusing Metric 'Half-Kilo' with International Pound
In informal European speech, a 'pound' is sometimes called 500 g. The legal international avoirdupois pound is exactly 453.59237 g — a ~10% discrepancy.
Avoid : Confusing Avoirdupois Ounces with Troy Ounces
Standard commercial goods use avoirdupois ounces (28.3495 g). Gold, silver, and precious metals use troy ounces (31.1035 g), which are about 9.7% heavier.
Avoid : Forgetting That 1 Stone Equals 14 Pounds
The British stone is not decimal: 1 stone = 14 pounds = 6.35029 kg. A weight of 10.5 stones equals 10 stone 7 lbs (66.68 kg).
Frequently asked questions
Answers to the questions people ask about Weight Converter.
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Updated on August 2026. See all tools