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Lb vs. Lbf: What's the Difference?

Edited by Aimie Carlson || By Janet White || Published on February 25, 2024
"Lb" stands for pound, a unit of mass in the imperial system, while "lbf" stands for pound-force, a unit of force in the same system; lb measures mass, lbf measures force.

Key Differences

Lb (pound) is a unit of mass in the imperial system, commonly used in the United States for measuring weight. It measures the quantity of matter in an object. In contrast, lbf (pound-force) is a unit of force in the same system, measuring the amount of force exerted on an object, typically due to gravity.
When using lb, one is referring to the mass of an object, which remains constant regardless of location. For example, a 5 lb weight always has a mass of 5 lbs. However, when referring to lbf, it's about the force exerted by the mass; the force can vary based on the acceleration due to gravity.
In daily use, especially in non-scientific contexts, lb is often used interchangeably with weight, though technically it measures mass. Lbf, while less commonly used in everyday language, is more accurate when discussing weight as a force, such as in engineering and physics contexts.
Lb is part of the widely used imperial system of measurements, which includes other units like ounces and tons. The use of lbf is more specialized, often seen in technical fields like mechanics and aerospace where precise measurements of force are crucial.
The distinction between lb and lbf becomes important in fields like physics and engineering, where precise measurements are necessary. In everyday use, however, the distinction is often overlooked, with lb serving as a general measure of weight.

Comparison Chart

Type of Measurement


Constant or Variable

Constant (same everywhere)
Variable (depends on gravity)

Common Usage

Measuring weight (mass)
Measuring force (weight as a force)

System of Units

Imperial System
Imperial System


General use, including commerce and daily life
Technical fields like engineering and physics

Lb and Lbf Definitions


Commonly used to indicate weight in everyday language.
She lost 15 lbs on her new diet.


Used in physics to describe force exerted by mass.
In this equation, we will measure force in lbf.


Used for measuring food items in stores.
Apples are $1.20 per lb.


Indicates force that varies with gravitational pull.
The astronaut's equipment was tested under different lbf levels.


A standard unit for commercial and personal use.
He bought 5 lbs of flour for baking.


Essential for precise force calculations in engineering.
The bridge's load capacity is calculated in lbf.


A measurement of mass in the imperial system.
The package weighs 10 lbs.


A unit of force in the imperial system.
The engine has a thrust of 500 lbf.


A term used to describe the physical quantity of matter in an object.
This dumbbell is 20 lbs.


Used in technical and mechanical specifications.
This bolt can withstand a force of up to 200 lbf.


A pound (unit of weight).


Pound-force (unit of force)


(cricket) leg bye


16 ounces;
He tried to lift 100 pounds


What does lbf measure?

Lbf measures force, specifically pound-force.

Can lb be used to measure liquids?

Yes, lb can be used for liquids, but usually measured in volume.

Is lb used globally?

Lb is used primarily in countries using the imperial system.

Can lbf change with location?

Yes, since lbf is affected by gravitational pull.

Is lbf used in automotive specifications?

Yes, lbf is often used in automotive specs, like engine torque.

Are lb and lbf interchangeable?

No, they measure different things: mass and force.

Is lb the same as pounds?

Yes, lb is the abbreviation for pounds.

How do you convert lb to kilograms?

Multiply the pounds by 0.453592 to get kilograms.

What is a common use of lb in daily life?

Lb is commonly used to measure body weight.

Why is lbf important in physics?

Lbf helps in accurately calculating forces and motion.

How do you measure lb?

Lb is measured using scales and balances.

Is knowledge of lb and lbf necessary for engineers?

Yes, engineers often need to understand both lb and lbf for accurate measurements in their work.

Do scientists use lbf?

Yes, particularly in fields like physics and engineering.

Can lb be used in scientific research?

Yes, but the metric system is more commonly used in science.

How is lb used in the food industry?

Lb is used for pricing and packaging food products.

Is lbf important in aerospace?

Yes, lbf is crucial in calculating forces in aerospace engineering.

Do lb and lbf have the same value on Earth?

Practically, they are often treated as equivalent on Earth.

Can lb be converted to Newtons?

No, but lbf can be converted to Newtons for force measurement.

What's the symbol for lbf?

The symbol for lbf is "lbf".

Are lb and lbf part of the metric system?

No, they are part of the imperial system.
About Author
Written by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.
Edited by
Aimie Carlson
Aimie Carlson, holding a master's degree in English literature, is a fervent English language enthusiast. She lends her writing talents to Difference Wiki, a prominent website that specializes in comparisons, offering readers insightful analyses that both captivate and inform.

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