Unit Convertor

1 Conversion of Physical (Measurable) Dimensions

Physical dimensions, such as mass, volume, time, temperature, and distance, are all properties that can be measured. Depending on the context of what is being measured, different units are more appropriate than others. For example, the height of a person is best measured in feet and inches, or meters, rather than kilometers or miles. Table 1 through Table 5 contain common unit conversions for mass, volume, time, temperature, and distance respectively.

Table 1: Conversion factors for common mass units

For example:

3 tn=3 tn*((907,185 g)/(1 tn))=2,721,555 g.

Similarly:

1,000 lbs=1,000 lbs*((1 t (metric))/(2,205 lbs))≅0.454 t (metric).

Table 2: Conversion factors for common volume units

For example:

2 gal=2 gal*((1 gal)/(7.5 ft³ ))=0.268 ft³.

Similarly:

2,500 fl oz=2,500 fl oz*((1 bbl)/(5,376 fl oz))≅0.465 bbls.

Table 3: Conversion factors for common temperature units

For example:

25 °C=(25 °C*9/5)+32=77 °F.

Similarly:

300 K=300 K-273=27°C.

Table 4: Conversion factors for common time units

For example:

360 s=360 s*((1 min)/(60 s))=6 min.

Similarly:

3 yrs=3 yrs*((52 wks)/(1 yr))=156 wks.

Table 5: Conversion factors for common distance (length) units

For example:

48 in=48 in*((1 yd)/(36 in))≅1.33 yds.

Similarly:

3 mi=3 mi*((5,280 ft)/(1 mi))=15,840 ft.

1.1 Metric Unit Prefixes

For measurements given in the metric (SI) system, such as meters, units can be easily converted to other SI measurements using a set of pre-defined prefixes. For example, the prefix kilo- means one-thousand times larger, so a kilo-meter (kilometer) is 1,000 meters. Common prefixes for the metric system are shown in Table 6 below.

Table 6: Common prefixes used to convert between metric units of measurement

2 Conversion of Energy Units

Different sources of energy (e.g. fuels) are often reported with different units of measurement, typically with reference to their volume or mass. To make a proper comparison between fuels, we have to convert their reported values to a common energy unit.

2.1 Energy Base Units

Different industries (and parts of the world) use different energy units, which may also depend on the primary source, or secondary use of the energy. The most commonly used energy units are kilowatt-hours (kWh), British thermal units (Btu), and gigajoules (GJ). Table 7 contains the conversion factors used to switch between these base units.

Table 7: Conversion factors for energy base-units

For example:

1,000 kWh=1,000 kWh*((1 GJ)/(278 kWh))≅3.6 GJ.

Similarly:

0.01 GJ=0.01 GJ*((947,817 Btu)/GJ)≅9,478 Btu.

Typically, kWh are used to quantify electrical energy (i.e. electricity), GJ are used to quantify natural gas consumption, and Btu are used in the heating industry, e.g. for furnaces and heat pumps. It is important to note, however, that any of the above units may be used when referring to energy.

2.2 Heat Content of Common Fuels

Different fuels have different heat contents, often reported in energy per unit-mass (e.g. GJ/kg), or energy per unit-volume (e.g. kWh/m³ ). For this reason, a kilogram of gasoline does not have the same amount of energy as a kilogram of diesel, or a kilogram of wood. Similarly, in terms of heat content, a litre of propane is not equivalent to a litre of natural gas. Table 8 contains the estimated heat content of various fuels, given in both their reported units, as well as common volume- and mass-based units for easy comparison.

Table 8: Heat content for various types of fuel

For example, we can show that a kilogram of hydrogen has over 2 and half-times the heat content of a kilogram of natural gas:

(0.1200 GJ/kg_Hydrogen)/(0.0459 GJ/kg_{Natural Gas} )≅2.6.

---

a. Lower heating values (LHV)
b. Source: The Energy and Fuel Data Sheet, Ian Staffell, University of Birmingham, UK
c. Source: Forest Research, United Kingdom
d. Equivalent to 128 cubic-feet
e. Source: World Nuclear Association
f. CANDU fuel bundles are roughly 20 kg, and up to 6,500 can be used in a typical reactor (Wikipedia)

2.3 Thermal Efficiency

Oftentimes, we do not burn fuels just for the sole purpose of releasing heat. For example, we burn gasoline and diesel in internal combustion vehicles (ICEVs) to transport ourselves and our belongings between two locations. Similarly, power plants burn coal or gas in order to generate electricity. Different processes use the heat from combustion at varying levels of efficiency and, as a result, energy is lost/wasted along the way.

2.3.1 Space heating efficiency

The efficiency of a space heating system is defined as the useful heating energy provided by the system, divided by the heat content of the fuel supply. Different fuels can be more or less efficient depending on a number of factors, such as the type and age of the technology, and how well the system has been insulated. Table 9 contains typical ranges of heating efficiencies for different fuels and system types.

Table 9: Range of thermal efficiencies of different space-heating systems