Calories to Quads (cal to quad)

1 calorie equals 3.965666831×10⁻¹⁸ quads (rounded).

1 calorie = 3.965666831×10⁻¹⁸ quads

How to convert calories to quads

To convert calories to quads, multiply the number of calories by 3.965666831×10⁻¹⁸. The factor is rounded to 10 significant digits. To go the other way, multiply quads by 2.521644007×10¹⁷ (rounded).

quads = calories × 3.965666831×10⁻¹⁸

Example: 10 calories = 3.965666831×10⁻¹⁷ quads.

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

About these units

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)

Quad (quad)

US customaryTraditional unit (still used in some regions)

One quadrillion BTU (about 1.055×10¹⁸ J). Used to quote national and global energy use; US consumption was about 100 quads in 2005.

Energy planners reach for the quad when joules or gallons become unwieldy. One quad is a quadrillion (10 to the 15th power) British thermal units, a figure the US Department of Energy uses for national and world energy budgets. In SI terms it is about 1.055 exajoules, or 1.055 times 10 to the 18th joules.

Which BTU applies changes the last digits. The figure used here, 1.05505585 times 10 to the 18th joules, corresponds to the International Table BTU of roughly 1,055.06 J. The 59 degree Fahrenheit BTU used in American gas pricing would give a value about 0.02 percent smaller, and the Wikipedia article on the quad does not say which BTU it assumes.

For scale, one quad equals about 8 billion US gallons of gasoline or roughly 293 terawatt-hours of electricity. Wikipedia reports world primary energy production of about 638 quads in 2022. In 2005 the US economy used close to 100 quads, so the unit suits country-sized totals rather than anything a household buys.

1 quad = 1.055055853×10¹⁸ joules (approximately).

Sources: Wikipedia: Quad (unit); EIA: British thermal units (Btu); Wikipedia: British thermal unit

Related conversions

See all energy units.