Conversion Tables & Mathematical Constants

The following information is based in large part on the published work of Barrie Lawson at and have in some cases been modified to reflect the differences between imperial units and U.S./SI units.

Conversion Table

1 KiloWatthour (kWh)=3.6 MegaJoules (MJ)
1 KiloWatthour (kWh)=3412 British Thermal Units (BTU)
1 KiloWatthour (kWh)=859.2 kilocalories (kcal)
1 Joule (J)=1 Watt Second
1 Joule (J)=1 Newton-Metre (N-m)
1 Joule (J)=0.1026 Metre-Kilogram (mkg)
1 Joule (J)=6.24 x 1012 Million electronVolts (MeV)
1 GigaJoule (GJ)=277.8 KiloWatthours (kWh)
1 Calorie (cal)=4.19002 Joules (J)
1 British Thermal Unit (BTU)=1055 Joules (J)
1 Therm=100,000 BTU
1 Therm=29.3 kWh
1 Quadrillion BTU (Quad)=1015 BTU
1 Quadrillion BTU (Quad)=2.931 x 1011 KiloWatthours (KWh)
1 Quadrillion BTU (Quad)=293.1 TeraWatthours (TWh)
1 Ton of Oil Equivalent (toe)=42 GigaJoules (GJ)
1 Ton of Oil Equivalent (toe)=11.6 MegaWatthours (MWh) [See Note 1 below] 1 GigaWatthour (GWh)=86 Tons of Oil Equivalent (toe)
1 TeraWatthour (TWh)=1 Billion KiloWatthours (KWh)
1 Electron Volt (eV)=1.6 X 10-19 Joules (J)
1MeV=1.07 X 10-3 amu (Mass to Energy Conversion)

Energy Density / Calorific Content
1 KiloWatthour/Kilogram (kWh/Kg)=3.6 GigaJoules/tonne (GJ/tonne)

1 Watt (W)=1 Joule/Second (J/s)
1 Watt (W)=3.7 BTU per hour (BTU/h)
1 Watt (W)=668 Lumens [See Note 2 below] 1 kiloWatt (kW)=1000 Watts (W)
1 MegaWatt (MW)=1000 kiloWatts (kW) [See Note 3 below] 1 Horse Power (hp)=746 Watts (W)
0 decibel (dB)=1 Power ratio (Note logarithmic scale)
3 dB=2 Power ratio
10 db=10 Power ratio
1 milliWatt (mW)=0 dBm Relative power (Note logarithmic scale)
100 milliWatts (mW)=20 dBm
1 microWatt (µW)=-30 dBm
1 femto Watt (fW)=10-15 Watts

1 metre per second per second (m/s2)=3.281 feet per second per second (ft/s2)

Gravitational Constant (G) (At the Earth’s surface)
9.80665 (m/s2)=32.174 (ft/s2)

1 Imperial Ton (t)=2240 Pounds (lb)
1 US Ton (t)=2000 Pounds (lb)
1 Kilogram (Kg)=2.2 Pounds (lb)
1 Kilogram (Kg)=9.807 Newtons (N) On the Earth’s surface
1 Stone=6.35 Kilograms (Kg)
1 Ounce (Oz)=28.35 Grams (g)
1 Atomic Mass Unit (amu)=1.67377 X 10-27 Kilogram (Kg)
1 Atomic Mass Unit (amu)=931.5 MeV (Mass to Energy Conversion)

1 Newton (N)=0.102 Kilograms-Force (kgf)
1 Newton (N)=0.22 Pound-Force (lbf)
1 Poundal=0.138 Newtons (N)
1 Poundal=0.031 Pound-Force (lbf)

1 Newton-Metre (N.M)=0.102 kilogram-Force.Metres (kgf.m)
1 Newton-Metre (N.M)=0.738 FootPounds-Force (ft.lbf)

Electric Charge
1 Coulomb (C)=6.25 X 1018 Electrons (e)
1 AmpHour (Ah)=3600 Coulombs (C)

Electric Current
1 Amp (A)=1 Coulomb per Second (C/s)

Electric Voltage
1 Volt (V)=1 Joule per Coulomb (J/C)

Frequency / Wavelength
1 MegaHertz (MHz)=300 metres (M)

Flow Rate
1 Litre per Second=792 Gallons (Imp) per Hour (gal/hr)

1 Mile=1.6 Kilometers (km)
1 Metre (m)=39.4 Inches (in)
1 Inch (in)=2.54 centimetres (cm)
1 Thousandth of an Inch (thou)=25.4 Microns
1 Micrometre (Micron)=10-3 (0.001) Millimetres (mm)
1 Nanometre=10-6 Millimetres (mm)
1 Angstrom=10-7 Millimetres (mm)
Atomic Diameter=1 Angstrom (Approximately)
1 Nautical Mile (nm)=1.1508 Miles (m)

1 Square Metre (m2)=10.76 Square Feet (sq.ft)
1 Hectare (ha)=10,000 Square Metres (m2)
1 Hectare (ha)=2.47 Acres (acre)
1 Acre (acre)=4840 Square Yards (sq yd)
1 Square Mile (mile2)=640 Acres (acre)
1 Square Mile (mile2)=2.59 Square Kilometres (km2)
1 Square Kilometre (km2)=100 Hectares (ha)

1 Cubic Metre (m3)=1,000 Litres (l)
1 Litre (l)=1,000,000 (mm3)
1 Gallon (Imperial) (gal)=4.55 Litres (l)
1 Gallon (Imperial) (gal)=1.2 Gallons (US) (gal)
1 Barrel (US Oil) (bbl)=42 Gallons (US Liq) (gal)

1 Metre per second (m/s)=2.24 miles per hour (mph)
1 Mile per Hour (mph)=1.61 Kilometres per Hour (km/hr)
1 Knot (knot)=1.15 Miles per Hour (mph)

Rotational Speed
1 Revolution per minute (rpm)=0.105 Radians per second (rad/sec)

1 bar or atm (atmospheric pressure)=14.5 Pounds per Square Inch (psi)
1 bar=100,000 Pascals (Pa)
1 Pound per Square Inch (psi)=6895 Newtons per Square Meter (N/m2)
1 Pascal (Pa)=1 Newton per Square Meter (N/m2)
1 Megapascal (MPa)=145 Pounds per Square Inch (psi)

Fuel Consumption
30 Miles per Gallon (Imperial)(mpg)=9.42 Litres/100 Kilometers (l/100km)

Radiation Activity (Radiotiactive Decay)
1 Becquerel (Bq)=Material quantity producing 1 Nuclear decays/second
1 Curie (Ci) (Obsolete)=3.7 X 1010 Becquerel (Bq)

Radiation Dose
1 Gray (Gy)=1 Joule/Kilogram (J/Kg)
1 Radiation Absorbed Dose (rad)(Obsolete)=0.01 Gray (Gy)
1 Röntgen (R) (Obsolete)=258 X 10-6Coulombs per Kilogram of Air (C/Kg)
1 Gray (Gy)=115 Röntgen (R)
1 Sievert (Sv)=1 Gray X Q (Gy) [See Note 4 below] 1 Röntgen Equivalent Man (rem) (Obsolete)=0.01 Sieverts (Sv) [See Note 4 below]

Avogadros Number (NA)=6.02214179 X 1023
1 Mole (n)=Contains NA particles

Other Equivalents
1 Metric Ton of Oil (ton)=7.64 Barrels (bbl)

Note 1: 1 toe is the quantity of oil which has the equivalent energy content of 11.6 MWh of electricity. It is not the quantity of oil necessary to produce 11.6 MWh of electricity. The amount of oil consumed in producing 11.6 MWh of electrical energy may be more than three times as much due to the inefficiency of the conversion process.

Note 2: A light flux of 668 Lumens is equivalent to an energy flow rate of 1 Watt of radiant electrical (or other) power. It is not the light flux produced by 1 Watt of electricity. An incandescent light bulb typically converts less than 10% of its input electrical energy into light. The rest is lost as heat See Energy Efficiency .

Note 3: The power in MegaWatts of an electricity generating plant may be expressed as MWe or MWt (alternatively MWth). MWe is the more common and represents the electrical output power of the plant. MWt is the thermal input power developed by the furnace or nuclear reactor. The output power MWe is generally only about 30% or 40% of the input power MWt.

Note 4: I Sievert = I Gray X Q where the quality factor (Q)is a measure of the magnitude of the damage done by the dose. The Gray is the dose, the Sievert is the effect of the dose.
Similarly 1 rem = 1R X Q.

Orders of Magnitude

Yotta 1024 Septillion
Zetta 1021 Sextillion
Exa 1018 Quintillion
Peta 1015 Quadrillion
Tera 1012 Trillion
Giga 109 Billion
Mega 106 Million
Kilo 103 Thousand
Hecto 102 Hundred
Deka 101 Ten
One 100 One
Deci 10-1 Tenth
Centi 10-2 Hundredth
Milli 10-3 Thousandth
Micro 10-6 Millionth
Nano 10-9 Billionth
Pico 10-12 Trillionth
Femto 10-15 Quadrillionth
Atto 10-18 Quintillionth
Zepto 10-21 Sextillionth
Yocto 10-24 Septillionth

Constants and Definitions

Some Physical Constants

Speed of Light (c)=300 X 106 metres/second (m/s)

Permeability of vacuum (μ0)=4π X 10-7 Newtons/square Ampere (N/A2) or Henries/metre (H/m)

Permitivity of vacuum (ε0)=8.8 X 10-12 Farads/metre (F/m)

1 Mole – (mol)=A unit representing an amount of substance which contains 6.022 X 1023 entities (atoms, molecules, ions, electrons etc.)

Electron Charge (e)=1.6 X 10-19 Coulombs

Electron Mass=9.1 X 10-31 Kg

Faraday Constant (F)=The amount of electric charge in one mole of electrons NA X e = 9.650 X 104 Coulombs/mole (C/mol)

Avogadro’s Constant (NA)=The number of atoms in 12 grams of carbon-12 = ( 6.022 X 1023 ) Also – The number of entities in a mole of those entities.

Boltzmann’s Constant (k)=The kinetic energy of one molecule of an ideal gas = 1.38 X 10-23 Joules/degree Kelvin (J/K)

Universal Gas Constant (R)=The kinetic energy of one mole of an ideal gas = 8.31446 Joules/degree Kelvin (J/K)

Planck’s Constant (h)=6.63 X 10-34 Joule seconds (J·s)= 4.14 X 10-15 eV seconds (eV·s)