An avoirdupois pound is exactly 0.45359237 kilograms.
Pounds to Ounces Converter — lb to oz
Convert Pound (lb) to Ounce (oz) using the exact conversion factor (1 pound = 16 ounce). See the formula, worked examples, conversion table, unit comparison, history, and common uses.
Pounds to Ounces converter
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An avoirdupois ounce is 1/16 pound.
Result = input x 0.45359237 / 0.02834952313.
Mass uses the kilogram as the base unit.
Reserved above the conversion cards and below the converter.
About Converting Pounds to Ounces
Weight conversions between Pound and Ounce come up constantly in everyday commerce, shipping, and cooking, since US packaging is usually labeled in pounds while most of the rest of the world uses kilograms. Pound is typically associated with united States (primary mass/weight unit), while Ounce is typically associated with united States (cooking, postal, retail).
Formula
ounces = pounds × 16
This factor comes from each unit's defined relationship to the category's base unit: 1 pound equals 0.45359237 base units, and 1 ounce equals 0.028349523125 base units, so dividing one by the other gives the direct pound-to-ounce factor of 16.
Simple example
1 lb × 16 = 16 oz
1 pound = 16 ounces.
Real-world example
50 lb × 16 = 800 oz
50 pounds = 800 ounces.
Conversion table
| Pound (lb) | Ounce (oz) |
|---|---|
| 1 lb | 16 oz |
| 5 lb | 80 oz |
| 10 lb | 160 oz |
| 25 lb | 400 oz |
| 50 lb | 800 oz |
| 100 lb | 1,600 oz |
Reverse conversion: Ounce to Pound
16 oz × 0.0625 = 1 lb
16 ounces = 1 pound.
pounds = ounces × 0.0625
For a page dedicated to this direction, see Ounce to Pound.
Pound vs. Ounce
| Aspect | Pound | Ounce |
|---|---|---|
| Family | US/imperial customary unit | US/imperial customary unit |
| Typical use | Body weight and food retail packaging in the United States | US cooking and recipe measurement (small quantities) |
| Where it's used | United States (primary mass/weight unit) | United States (cooking, postal, retail) |
Understanding the Pound
Pound (lb) measures mass. The avoirdupois pound is legally defined as exactly 0.45359237 kilograms, fixed by international treaty in 1959. It is classified as a US/imperial customary unit.
Where it's used: United States (primary mass/weight unit) United Kingdom (informal and some retail use) Various Caribbean and Pacific territories with historical UK/US ties
Pound-mass vs. pound-force. This page converts pound-mass (lbm), a unit of mass. Pound-force (lbf) is a separate unit measuring the force gravity exerts on one pound-mass, used in engineering contexts like pounds per square inch.
Uses of the Pound today
- Body weight and food retail packaging in the United States
- Postal, parcel, and freight weight in US shipping and logistics
- Pound-force (lbf) and its derivatives (psi, foot-pounds) in US engineering and aerospace
History of the Pound
Unlike the kilogram's single documented birth in revolutionary France, the pound's history is a long, layered narrowing of competing regional standards. The avoirdupois pound — ancestor of today's standard — emerged among London merchants in the early 14th century (recorded use around 1303), used for weighing wool and other bulk goods under the system merchants called 'avoir de pois,' Old French for 'goods of weight.' Its 16-ounce structure suited large-scale trade better than the 12-ounce troy pound used for precious metals.
Wool merchants used a related 'wool pound' of about 6,992 grains — close enough to 7,000 that Elizabeth I's government formally fixed the avoirdupois pound at exactly 7,000 grains in 1588, the value still used today. Britain and the US then refined their physical standards separately over the following centuries, leaving small discrepancies between them.
Those discrepancies were resolved on 1 July 1959, when the US, UK, Canada, Australia, New Zealand, and South Africa signed the International Yard and Pound Agreement, fixing the pound at exactly 0.45359237 kg and the yard at exactly 0.9144 m. The US National Bureau of Standards (now NIST) adopted the value immediately; the UK followed via its Weights and Measures Act 1963 — the value used by virtually every country today.
Historical origin. Pound was not the invention of a single named person; it developed through the process described above.
Understanding the Ounce
Ounce (oz) measures mass. The avoirdupois ounce is 1/16 of a pound: exactly 28.349523125 grams. It is classified as a US/imperial customary unit.
Where it's used: United States (cooking, postal, retail) United Kingdom (informal/retail use)
Avoirdupois ounce vs. troy ounce. The everyday ounce (avoirdupois, 28.35 g) used for cooking and shipping is a different, smaller unit than the troy ounce (31.10 g) used for precious metals like gold and silver — this page uses the everyday avoirdupois ounce.
Uses of the Ounce today
- US cooking and recipe measurement (small quantities)
- US postal and shipping weight
- Precious metals (troy ounce, a related but distinct unit)
History of the Ounce
The ounce descends from the Roman 'uncia' (a twelfth part), inherited through medieval English weight systems; the avoirdupois ounce (for general goods, as opposed to the troy ounce for precious metals) became standard for everyday trade, fixed at exactly 28.349523125 g via the pound's 1959 international standardization.
Historical origin. Ounce was not the invention of a single named person; it developed through the process described above.
Pound — sources
- NIST — International yard and pound, Federal Register notice (1959) — Official 1959 refinement of the yard and pound values adopted by the US National Bureau of Standards.
- Encyclopaedia Britannica — 'Pound (unit of weight)' — History of the Tower, troy, and avoirdupois pounds and their standardization in England.
- UK Weights and Measures Act 1963, s.1(1) — Statutory UK definition of the pound as exactly 0.45359237 kilogram.
Ounce — sources
- NIST — International yard and pound (1959) — Basis for the modern ounce via the standardized pound.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many ounces are in 1 pound?
1 pound equals 16 ounces, using the exact defined conversion factor rather than an estimate.
How do I convert pound to ounce?
Multiply the pound value by 16. The converter above does this instantly to whatever precision you set.
How do I convert ounce back to pound?
Use the reverse factor: 1 ounce equals 0.0625 pounds. You can also use the swap control in the converter above to flip the direction instantly.
What is a pound?
Pound (lb) measures mass. The avoirdupois pound is legally defined as exactly 0.45359237 kilograms, fixed by international treaty in 1959. It is classified as a US/imperial customary unit.
What is a ounce?
Ounce (oz) measures mass. The avoirdupois ounce is 1/16 of a pound: exactly 28.349523125 grams. It is classified as a US/imperial customary unit.
Is the pound to ounce conversion exact?
Yes. The avoirdupois ounce is 1/16 of a pound: exactly 28.349523125 grams. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between pound-mass vs. pound-force?
This page converts pound-mass (lbm), a unit of mass. Pound-force (lbf) is a separate unit measuring the force gravity exerts on one pound-mass, used in engineering contexts like pounds per square inch.
Where is the pound still used today?
United States (primary mass/weight unit) United Kingdom (informal and some retail use) Various Caribbean and Pacific territories with historical UK/US ties