For an object at the Earth’s surface, multiply the mass (in pounds) by the “standard gravitational force” of 32.174049 (usually rounded to 32.174), to determine lbf (pound-force). A different ratio must be used if the object is not situated at the surface of the Earth.

## Calculate the mass.

Assuming the object is one that is at the surface of the Earth, calculate its mass in pounds.

## Add the gravitational force.

Calculate the mass by multiplying it by the “standard gravitational force,” which is 32.174 if the object is on the surface of the Earth.

## Determine the lbf.

The result of multiplying Steps 1 and 2 is the lbf, or “pound-force,” which is expressed in foot-pounds per second squared.

## Additional explanation

A “pound-mass” is a unit of mass, often known as a lbm. “Pound-force” is a unit of measurement for force. Although a pound is commonly used to refer to a unit of mass, the weight of an object varies based on the strength of gravity in a particular location.

Because of the decreased gravity on the moon, a rock that weighs a pound on Earth’s surface weighs less there. The rock’s bulk would stay the same, though.