## Calculators for energy used in the United States

Note: Btu is British thermal units.

## Measuring energy in food

*Food calories* are a measure of energy in food. One food calorie is equal to 1,000 calories, or 1 kilocalorie. For example, the energy in a 300 food-calorie ice cream cone is about the same as the amount of electricity required to light a 100-watt incandescent light bulb for 3.5 hours.

## Scientific notation explained

Scientific notation is a shorthand way of writing a number that has a lot of digits. For example, the number 525,000,000 could be written as 5.25E+08. The *+08* indicates the decimal should be moved eight places to the right. A negative number after the *E* means the decimal should be moved that number of places to the left. For example, 5.25E-03 is the same as 0.00525.

Common energy units | Scientific notation |
---|---|

British thermal unit (Btu) | 1.0 |

millions of Btu | 1.0E+06 Btu |

therm | 1.0E+05 Btu |

billions of Btu | 1.0E+09 Btu |

quad | 1.0E+15 Btu |

calorie | 1.0 calorie |

kilocalorie | 1.0E+03 calories |

food calorie | 1.0E+03 calories |

thermie | 1.0E+05 calories |

teracalorie | 1.0E+12 calories |

joule | 1.0 joule |

megajoule | 1.0E+06 joule |

gigajoule | 1.0E+09 joule |

terajoule | 1.0E+12 joule |

Watthour | 1.0 |

kilowatthour (kWh) | 1.0E+03 Watthour |

megawatthour (mWh) | 1.0E+06 Watthour |

gigawatthour (gWh) | 1.0E+09 Watthour |

terawatthour (tWh) | 1.0E+12 Watthour |

*Last updated: October 28, 2024, with preliminary data for 2023.*