Weight Converter
Convert pounds, ounces, stones, kilograms and more instantly. Real-time results across metric, US customary and scientific units.
About Weight Units in the US
The United States primarily uses the US customary system: pounds (lb) for body weight and produce, ounces (oz) for smaller quantities, and short tons for bulk goods. The metric system is dominant in science, medicine and manufacturing. One pound is exactly 0.45359237 kg; one US short ton equals 2,000 pounds.
From a 14–15 oz NFL football to 20-ton semi-trailers, or from milligrams of pharmaceuticals to millions of metric tons of grain shipped from the Midwest — weight conversions are central to American industry, sport and daily life.
Conversion Formula
All weight conversions are linear. Each unit has a fixed factor f (kilograms per unit). The general formula is:
Universal linear formula:
m_target = m_source × (f_source ÷ f_target)mtarget=msource×ftargetfsource
Where f_source is kg per source unit, and f_target is kg per target unit. The converter first converts to kg, then to the target unit.
Practical US Examples
NFL Football
An official NFL game ball weighs 14–15 oz (396–425 g, 0.875–0.9375 lb). Compare: baseball 5–5.25 oz, basketball 22 oz, bowling ball 14–16 lb.
Thanksgiving Turkey
Average US Thanksgiving turkey: 15–16 lb (6.8–7.3 kg). A 16 lb turkey = 256 oz = about 232 troy oz. USDA recommends 1 lb per person for a meal.
US Penny
Post-1982 penny: exactly 2.5 g (0.0882 oz, 0.00551 lb). A roll of 50 pennies = 125 g. One million pennies would weigh 2,500 kg (5,512 lb).
Space Shuttle Main Engine
Each SSME weighed ~3,177 kg (7,004 lb, 3.5 US tons). NASA's infamous metric-imperial mix-up in 1999 sent the Mars Climate Orbiter off course — a $327 million lesson in unit consistency.
How the Converter Works
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Enter the numeric weight value in the input field.
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Select the source unit from the dropdown — all 20 units available.
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The value converts to kilograms using the exact US/international factor.
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From kilograms, all other units are calculated simultaneously.
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Results appear instantly; key units top, expandable groups below.
Quick Reference Tips
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1 lb = 16 oz; 1 stone = 14 lb; 1 US short ton = 2,000 lb.
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1 kg ≈ 2.2046 lb — multiply kg by 2.2 for a quick estimate.
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Troy oz ≠ regular oz: oz t = 31.10 g vs oz = 28.35 g. Always specify for precious metals.
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US short ton (2,000 lb) ≠ metric ton (2,205 lb) ≠ UK long ton (2,240 lb).
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For pharmacy and lab work, grams and milligrams are standard even in the US.
Frequently Asked Questions
How many ounces in a pound?
There are exactly 16 avoirdupois ounces in 1 pound. Note that troy ounces (for precious metals) are different: 1 troy lb = 12 troy oz, and 1 troy oz = 31.10 g vs 28.35 g for a regular oz.
What is the difference between a US ton and a metric ton?
A US short ton = 2,000 lb (907.18 kg). A metric ton = 1,000 kg (2,204.6 lb). A UK long ton = 2,240 lb (1,016 kg). The metric ton is about 10% heavier than a US ton — significant in bulk commodity contracts.
How many pounds are in a kilogram?
Approximately 2.20462 pounds in 1 kilogram. Exact: 1 lb = 0.45359237 kg. Quick mental math: double the kg and add 10% (e.g., 50 kg → 100 + 10 = 110 lb).
What does stone mean as a unit of weight?
One stone = 14 lb (6.35 kg). Still common in the UK and Ireland for body weight, but rarely used in the US. A 180 lb American is 12 stone 12 pounds in British terms.
Why is gold measured in troy ounces?
The troy ounce (31.10 g) predates the modern pound and derives from medieval Troyes trade standards. It is heavier than the regular ounce (28.35 g). All precious metals use troy weight globally for a consistent commodity market standard.
How much does the Earth weigh?
Earth's mass is ~5.9722 × 10²⁴ kg, or about 1.317 × 10²⁵ lb, or 6.587 × 10²¹ US tons. The mass is determined by observing gravitational effects on the Moon and satellites using Newton's law of gravitation.
All conversion factors follow US definitions and international NIST/BIPM standards. Particle masses use CODATA 2018. Astronomical masses use IAU 2012 values.