Engineering Unit Abbreviations
103 abbreviations · part of Units of Measurement Abbreviations
Abbreviations for units of power, energy, pressure, temperature, electricity, frequency, speed, flow, sound, light, force, torque and radiation, as they appear on spec sheets, utility bills, tire placards, HVAC equipment and car reviews. Many mix SI and US customary units (psi, BTU, hp, cfm), and capitalization carries meaning: kW is kilowatts of power while kWh is kilowatt-hours of energy, and mW and MW differ by a factor of a billion.
| Abbreviation | Stands for | Description |
|---|---|---|
| A | Ampere | The SI base unit of electric current, the flow of one coulomb of charge per second. |
| AFUE | Annual Fuel Utilization Efficiency | The percentage of a furnace's or boiler's fuel energy that becomes useful heat over a typical year. |
| Ah | Ampere-hour | Charge capacity of one ampere flowing for one hour, the rating for car, marine, deep-cycle, e-bike and solar storage batteries. |
| atm | Standard atmosphere | A pressure unit defined as exactly 101,325 pascals, approximately the average air pressure at sea level. |
| AWG | American wire gauge | Standard system for specifying the diameter of round electrical wire in North America, in which larger gauge numbers mean thinner wire. |
| bar | Bar | A metric pressure unit of 100,000 pascals, almost exactly standard atmospheric pressure. |
| bhp | Brake horsepower | Engine power measured at the crankshaft, before transmission and drivetrain losses, using a dynamometer brake. |
| BTU | British thermal unit | Heat needed to raise one pound of water by one degree Fahrenheit, about 1,055 joules. |
| C | Degree Celsius | The temperature scale for weather, cooking and medicine in nearly every country except the US. |
| Cal | Food Calorie (kilocalorie) | The "large calorie" used for food energy, equal to 1,000 small calories or one kilocalorie (4.184 kJ). |
| cfm | Cubic feet per minute | Volume flow rate of air or gas, used for HVAC airflow, bathroom and range-hood fans, air compressors, dust collectors and leaf blowers. |
| Ci | Curie | An older unit of radioactivity equal to 3.7 × 10^10 decays per second, roughly the activity of one gram of radium-226. |
| CID | Cubic inch displacement | Engine size measured as the total swept volume of all cylinders in cubic inches, the traditional American way of naming V8s such as the 350, 427 and 454. |
| CRI | Color Rendering Index | A score up to 100 measuring how accurately a light source shows colors compared with a reference source such as daylight. |
| dB | Decibel | A logarithmic unit expressing ratios of power or intensity, best known for sound levels. |
| dBA | A-weighted decibels | Sound level measured with a filter that mimics the human ear's lower sensitivity to very low and very high frequencies. |
| dBm | Decibel-milliwatts | Power level in decibels relative to one milliwatt, used for radio transmitters, Wi-Fi and cellular signal strength, and fiber-optic links. 0 dBm equals 1 mW, 20 dBm… |
| F | Degree Fahrenheit | The temperature scale used in the United States for weather, cooking and body temperature, on which water freezes at 32°F and boils at 212°F at sea level. |
| fc | Foot-candle | US unit of illuminance equal to one lumen per square foot, about 10.76 lux. |
| fpm | Feet per minute | A US unit for slower speeds such as air velocity in ducts, elevator travel, conveyor belts and aircraft climb or descent rates. |
| fps | Feet per second | A US customary speed unit used in ballistics, fluid flow and engineering. |
| ft-lb | Foot-pound | A US unit of work or energy, the energy needed to lift one pound by one foot, about 1.356 joules. |
| g | Standard gravity (g-force) | Acceleration expressed as a multiple of standard gravity, 9.80665 m/s². |
| ga | Gauge | A sizing number for sheet metal, wire, needles and shotguns whose meaning depends on the system: for sheet steel and wire a higher gauge is thinner, while shotgun gauge… |
| GHz | Gigahertz | One billion hertz, the unit for processor clock speeds, Wi-Fi bands (2.4, 5 and 6 GHz), 5G networks and microwave ovens, which operate at about 2.45 GHz. |
| GPa | Gigapascal | Billions of pascals: the unit for the stiffness (Young's modulus) of materials and for extreme pressures in geophysics. |
| gph | Gallons per hour | Flow rate in US gallons per hour, used for the fuel burn of boats, generators and aircraft, aquarium and pond pumps, and drip irrigation. |
| gpm | Gallons per minute | Flow rate in US gallons per minute, used for pumps, well yields, plumbing fixtures, irrigation and fire hoses. |
| GW | Gigawatt | A billion watts: the scale of large power stations, national grid capacity and major infrastructure projects. |
| GWh | Gigawatt-hour | A million kilowatt-hours, used for battery factory output, large storage projects and the annual generation of individual power plants. |
| hp | Horsepower | Traditional unit of engine and motor power in the US and UK, about 746 watts for mechanical horsepower. |
| hPa | Hectopascal | Weather forecasts and aviation outside North America give atmospheric pressure in hectopascals, each 100 pascals. |
| HRC | Rockwell hardness C (scale) | Hardness measured on the Rockwell C scale by pressing a diamond cone into a material under a 150-kilogram-force load and measuring how deeply it penetrates. |
| Hz | Hertz | The SI unit of frequency, one cycle per second. |
| in-lb | Inch-pound | A small US torque unit, one pound of force at one inch, one twelfth of a lb-ft or about 0.113 N·m. |
| inH2O | Inches of water column | A small pressure unit equal to a one-inch column of water, about 249 pascals. |
| inHg | Inches of mercury | Pressure unit used in US weather reports and North American aviation altimeter settings, based on the height of mercury in a barometer. |
| J | Joule | The SI unit of energy, work and heat: the work done by a force of one newton over one meter, or one watt for one second. |
| K | Kelvin | The SI base unit of temperature, counted from absolute zero, the coldest possible temperature. |
| kcal | Kilocalorie | A thousand calories, identical to the food Calorie and about 4.184 kilojoules. |
| kgf | Kilogram-force | The force of gravity on one kilogram at standard gravity, exactly 9.80665 newtons. |
| kHz | Kilohertz | One thousand hertz, the range of audible sound, AM radio frequencies and audio sampling. |
| kJ | Kilojoule | A thousand joules, the energy unit on food labels in Australia, New Zealand and the EU (alongside kcal) and in chemistry and physics problems. |
| km/h | Kilometers per hour | The SI-accepted unit for road speed in most of the world, shown on speed-limit signs, car speedometers and weather reports. |
| km/L | Kilometers per liter | Fuel economy as distance per liter, the form used in India, Japan, much of Southeast Asia and parts of Latin America. |
| kmph | Kilometers per hour | A variant of km/h widely used in India, on Indian Railways timetables, road signs and news, and in some other South Asian countries. |
| kn | Knot | One nautical mile per hour, exactly 1.852 km/h or about 1.151 mph, the standard speed unit for shipping, sailing, aviation and marine weather. |
| kPa | Kilopascal | Tire pressure, gas line pressure and barometric readings outside the US are often given in kilopascals, each 1,000 pascals. |
| kph | Kilometers per hour | Informal abbreviation for kilometers per hour, common in British, American and Australian journalism, motorsport commentary and casual writing, read aloud as "K-P-H". |
| ksi | Kilopounds per square inch | A thousand psi, the US unit for material strength and stress in structural and mechanical engineering. |
| kt | Knot (aviation) | The form of knot used in aviation, US weather products and many marine forecasts, often pluralized as kts. |
| kV | Kilovolt | One thousand volts, used for power lines, substations and X-ray equipment. |
| kVA | Kilovolt-ampere | One thousand volt-amperes, the usual rating for generators, distribution transformers, large UPS systems and industrial supplies. |
| kW | Kilowatt | Equal to 1,000 watts, the kilowatt rates engine output in most of the world, electric vehicle motors and chargers, home solar systems, heaters and appliances. |
| kWh | Kilowatt-hour | The unit on electricity bills: the energy used by a 1,000-watt load running for one hour, equal to 3.6 megajoules. |
| kWp | Kilowatt-peak | Rated output of a solar array under standard test conditions: 1,000 W/m² of sunlight at a cell temperature of 25°C. |
| L/100 km | Liters per 100 kilometers | Fuel consumption measure used in Europe, Canada, Australia and most metric countries: the liters of fuel a vehicle burns to travel 100 km. |
| lb-ft | Pound-feet | US unit of torque: one pound of force applied at a distance of one foot. |
| lbf | Pound-force | The force of gravity on one pound of mass at standard gravity, about 4.448 newtons. |
| lm | Lumen | The SI unit of luminous flux, the total visible light a source emits as perceived by the human eye. |
| lx | Lux | Illuminance, the amount of light falling on a surface, measured in lumens per square meter. |
| m/s | Meters per second | The SI unit of speed, used in physics, engineering, meteorology and athletics. |
| mA | Milliampere | One thousandth of an ampere, used for small electronic circuits, LEDs, sensors, USB current and battery drain. |
| mAh | Milliampere-hour | Electric charge unit used to rate the capacity of phone, earbud and power-bank batteries. |
| mbar | Millibar | One thousandth of a bar, equal to one hectopascal, the traditional unit of atmospheric pressure on weather maps. |
| MBH | Thousand BTU per hour | HVAC engineering shorthand for thousands of BTU per hour, using the Roman numeral M for thousand. |
| Mcf | Thousand cubic feet | The standard volume unit for natural gas production and sales in the US, with M as the Roman numeral for thousand. |
| MFD | Microfarad | An older marking for microfarads (millionths of a farad) still printed on motor run and start capacitors in air conditioners, furnaces and pumps. |
| MHz | Megahertz | One million hertz, used for FM radio (88 to 108 MHz), TV and cellular bands, and historically for processor clock speeds. |
| MJ | Megajoule | Fuel energy content, gas billing in some countries and engineering energy calculations are expressed in megajoules, millions of joules. |
| MMBtu | Million British thermal units | The standard pricing unit for natural gas in North American markets, equal to one million BTU or about 1.055 gigajoules. |
| mmHg | Millimeter of mercury | Pressure equal to the push of a 1 mm column of mercury, about 133.3 pascals. |
| MPa | Megapascal | Material strength, concrete grades, hydraulic systems and high-pressure gas use megapascals, millions of pascals. |
| MPG | Miles per gallon | Measure of fuel economy giving the distance a vehicle travels on one gallon of fuel. |
| MPGe | Miles per gallon equivalent | An EPA efficiency rating for electric and plug-in vehicles that treats 33.7 kWh of electricity as equal to the energy in one gallon of gasoline. |
| mph | Miles per hour | The unit for road speed limits, vehicle speeds and wind speeds in the United States and the United Kingdom. |
| mV | Millivolt | One thousandth of a volt, the scale of nerve and muscle signals, thermocouples, sensors and audio signals. |
| MW | Megawatt | Power plants, wind turbines, data centers and large industrial loads are rated in megawatts, millions of watts. |
| MWh | Megawatt-hour | Wholesale electricity prices, power-plant output and grid-scale battery storage are measured in MWh, each a thousand kilowatt-hours. |
| Nm | Newton-meter | Torque in SI units: the twisting effect of one newton applied one meter from an axis. |
| NPT | National Pipe Thread | US standard for tapered threads on pipes and fittings, in which the threads seal as they are tightened because the diameter changes by 1 in 16 along the length. |
| Pa | Pascal | The SI unit of pressure, one newton per square meter, a tiny amount: standard atmospheric pressure is 101,325 Pa. |
| ppb | Parts per billion | Concentration ratio of one part in a billion, used for trace contaminants such as lead and arsenic in drinking water, ozone in air and pesticide residues. |
| ppm | Parts per million | Concentration ratio of one part in a million, used for air pollutants, dissolved solids in water, carbon dioxide in the atmosphere and trace elements. |
| PS | Pferdestärke (metric horsepower) | Metric horsepower, defined as 75 kilogram-force meters per second, about 735.5 watts or 0.986 mechanical hp. |
| psi | Pounds per square inch | The US customary unit of pressure for tire inflation, air compressors, water pressure, scuba tanks and hydraulics. |
| psia | Pounds per square inch absolute | Pressure measured relative to a perfect vacuum, so the atmosphere at sea level reads about 14.7 psia. |
| psig | Pounds per square inch gauge | Pressure measured relative to the surrounding atmosphere, which is what ordinary gauges display: a flat tire reads 0 psig even though the air inside is at atmospheric… |
| R | Degree Rankine | An absolute temperature scale with Fahrenheit-sized degrees, starting at absolute zero: 0°R is −459.67°F and water freezes at 491.67°R. |
| rad | Rad (radiation absorbed dose) | An older unit of absorbed radiation dose equal to 0.01 gray, or 100 ergs per gram. |
| rem | Roentgen equivalent man | An older US unit of radiation dose equivalent, equal to 0.01 sievert. |
| RPM | Revolutions per minute | Rotational speed of an engine's crankshaft, shown on the tachometer in thousands. |
| SEER | Seasonal Energy Efficiency Ratio | The US efficiency rating for central air conditioners and heat pumps: seasonal cooling output in BTU divided by electricity used in watt-hours. |
| thm | Therm | Heat energy equal to 100,000 BTU, about 105.5 megajoules or 29.3 kWh, used to bill residential natural gas in the US. |
| toe | Tonne of oil equivalent | Energy unit used in international energy statistics, defined by the IEA as 41.868 gigajoules, roughly the energy in one tonne of crude oil. |
| TPI | Threads per inch | The number of thread crests per inch along a screw or bolt, the US way of specifying thread pitch. |
| TR | Ton of refrigeration | Cooling capacity equal to 12,000 BTU per hour, about 3.52 kW, used to size air conditioners and chillers in the US, India and elsewhere. |
| TWh | Terawatt-hour | National and global electricity statistics use TWh, one billion kilowatt-hours. |
| V | Volt | Electric potential difference, the "pressure" that drives current through a circuit, is measured in volts. |
| VA | Volt-ampere | Apparent power in AC circuits: voltage times current, without accounting for power factor. |
| W | Watt | The SI unit of power, one joule per second, measuring how fast energy is used or produced. |
| Wh | Watt-hour | Energy equal to one watt sustained for one hour, or 3,600 joules. |
| whp | Wheel horsepower | Power measured at the driven wheels on a chassis dynamometer, after transmission and drivetrain losses. |
More units of measurement abbreviations
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- US Customary and Imperial Unit Abbreviations (43)