The University of New Mexico

Units & Constants

 

NUMERIC PREFIXES

Abbreviation

Prefix

Numeric Value

a

atto-

10-18, one quintillionth

f

femto-

10-15, one quadrillionth

p

pico-

10-12, one trillionth

n

nano-

10-9, one billionth

m

micro-

10-6, one millionth

m

milli-

10-3, one thousandth

c

centi-

10-2, one hundredth

d

deci-

10-1, one tenth

dk

deka-

101, ten

h

hecto-

102, hundred

k

kilo-

103, thousand

M

mega-

106, million

G

giga-

109, billion

T

tera-

1012, trillion

P

peta-

1015, quadrillion

E

exa-

1018, quintillion

 

 

RADIATION UNITS

Measured property

“Old” unit

“New” SI unit

Conversion factor

Radioactivity

curie (Ci) = 3.7 X 1010 dps

curie (Ci) = 2.22 X 1012 dpm

becquerel (Bq) = 1 dps

1 Ci = 3.7 X 1010 Bq

1 Bq = 2.7 X 10-11 Ci

Radiation exposure

roentgen (R) = 2.58 10-4 C/kg

coulomb/kg (C/kg)

1 R = 2.58 X 10-4 C/kg

1 C/kg = 3.88 103 R

Radiation absorbed dose

rad = 100 erg/g

gray (Gy) = 1 J/kg

1 rad = 0.01 Gy

1 rad = 1 cGy

1 Gy = 100 rad

Radiation dose equivalent

rem = QF X rad

sievert (Sv) = QF X Gy

1 rem = 0.01 Sv

1 rem = 1 cSv

1 Sv = 100 rem

dps = disintegration per second

dpm = disintegration per minute

QF = quality factor


UNITS AND CONSTANTS

Energy

1 electron volt (eV)

= 1.602 X 10-12erg

1 kiloelectron volt (keV)

= 1.602 X 10-9 erg

1 million electron volts (MeV)

= 1.602 X 10-6 erg

1 joule (J)

= 107 ergs

1 watt (W)

= 107ergs/sec

1 rad

= 1 X 10-2 J/kg

1 gray (Gy)

= 100 rad

= 1 J/kg

1 sievert (Sv)

= 100 rem

= 1 J/kg

1 horsepower (HP)

= 746 W

1 calorie (cal)

= 4.184 J

Charge

1 electronic charge

= 4.8 X 10-10 electrostatic unit

= 1.6 X 10-19 C

1 coulomb (C)

= 6.28 X 1018 charge

1 ampere (A)

= 1 C/s

Mass and energy

1 atomic mass unit (amu or u)

= 1.66 X 10-24g

= 1/12 the atomic weight of 12C

= 931 MeV

1 electron rest mass

= 0.511 MeV

= 0.000549 amy

1 proton rest mass

= 938.78 MeV

= 1.007277amu

1 neutron rest mass

= 939.07 MeV

= 1.008665 amu

1 pound

= 453.6 g

Length

1 micrometer or micron (mm)

= 10-6 meter

= 104 D

1 nanometer (nm)

= 10-9 meter

1 angstrom (D)

= 10-8 cm

1 fermi (F)

= 10-13 cm

1 inch

= 2.54 cm

Constants

Avogadro’s number

= 6.02 X 1023 atoms/g@atom

= 6.02 X 1023 molecules/g@mole

Planck’s constant (h)

= 6.625 X 10-27 erg@s/cycle

Velocity of light

= 3 X 1010 cm/sec

p

= 3.1416

e

= 2.7183