Foot-pounds to Calories (ft⋅lbf to cal)

1 foot-pound equals 0.3240482668 calories (rounded).

1 foot-pound = 0.3240482668 calories

How to convert foot-pounds to calories

To convert foot-pounds to calories, multiply the number of foot-pounds by 0.3240482668. The factor is rounded to 10 significant digits. To go the other way, multiply calories by 3.085960033 (rounded).

calories = foot-pounds × 0.3240482668

Example: 10 foot-pounds = 3.240482668 calories.

The 'calorie' on food labels is really a kilocalorie. The thermochemical calorie (4.184 J) is used here unless marked IT.

About these units

Foot-pound (ft⋅lbf)

US & ImperialCurrent unit

The work done by a force of one pound-force over one foot: about 1.35582 joules. Used for torque and energy in US engineering and ballistics.

Foot-pound hides a trap: the same words name two different things. As energy, a foot-pound is what a force of one pound-force transfers when it acts through a distance of one foot, about 1.355818 J. As torque, usually called the pound-foot, it is dimensionally the same but physically distinct, since energy is a scalar and torque is a vector, which is why careful writers specify foot-pound of energy or of torque.

The unit is tied to the early history of energy. In 1850 James Prescott Joule published a refined value of 772.692 foot-pounds of work per British thermal unit, which was the key figure in his demonstration that work converts to heat at a fixed rate. The same system defines the mechanical horsepower as 550 foot-pounds per second.

Today American ballistics is the best-known user. Muzzle energy of a bullet is commonly stated in foot-pounds, and a figure of about 7 kJ for an elephant gun, which is roughly 5,200 foot-pounds, shows the typical range for large rifle cartridges.

1 foot-pound = 1.355817948 joules (approximately).

Sources: Wikipedia: Foot-pound (energy); Wikipedia: James Prescott Joule; Wikipedia: Orders of magnitude (energy)

Calorie (cal)

ScientificTraditional unit (still used in some regions)

The thermochemical calorie: exactly 4.184 joules, the energy to raise one gram of water by one degree Celsius. Not the same as the food Calorie, which is a kilocalorie.

Latin calor, meaning heat, supplied the name. Nicolas Clement used it in lectures on heat engines between 1819 and 1824, and by 1852 Pierre Favre and Jean Silbermann applied it to the small unit based on a single gram of water warmed by one degree Celsius. Because the specific heat of water varies slightly with temperature, early calories differed from one laboratory to the next. A mean value near 4.1855 J was published for the 15 degree calorie in 1950, with an uncertainty of 0.0005 J.

Chemists settled the matter by definition. The thermochemical calorie is exactly 4.184 J, which is the figure used here, and NIST lists it with that exact value. The calorie is not an SI unit and is regarded as obsolete, since the ninth General Conference on Weights and Measures in 1948 preferred the joule for heat. One thousand of these calories make a kilocalorie, the larger unit used for food, and a slightly larger calorie, the International Table version of 4.1868 J, is used in steam tables.

1 calorie = 4.184 joules (exactly).

Sources: Wikipedia: Calorie; NIST SP 811, Appendix B.8 (energy conversion factors)

Related conversions

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