SI Base Units
Mass
kilogram
Length
meter
Time
second
Electric
Current
ampere
Luminous
Intensity
candela
kg
m
s
A
Temperature
kelvin
K
cd
Amount of
Substance
mole
mol
SI Derived Units
kg m2s-2
Energy
joule
J
kg m s-3
Power
watt
W
s-1
Activity
becquerel
Bq
m2s-1
Absorbed Dose
gray
Gy
m2s-2
Dose Equivalent
sievert
Sv
kg m s-2
Force
newton
N
kg m-1s-2
Pressure
pascal
Pa
kg m2s-3 A-1
Electric Potential
volt
V
kg-1 m2s4 A2
Capacitance
farad
F
kg-1 m2s3 A2
Conductance
siemens
S
kg s-2 A-1
Conductance
siemens
S
S
Coordinated Time
international atomic time
TAI
s-1
Frequency
hertz
Hz
S A
Electric charge
coulomb
C
kg m2s-3A-2
Resistance
ohm
W
kg m2s-2A-1
Magnetic Flux
weber
Wb
kg m2s-2A-2
Inductance
henry
H
K
Celsius
Temperature
0Celsius
0C
cd sr
Luminous Flux
lumen
lm
m-2cd sr
Illuminance
lux
lx
sr:  the steradian is the supplementary
SI unit of solid angle (dimensionless)
rad:  the radian is the supplementary
SI unit of plane angle (dimensionless)
Electromagnetic
measurement units
Health related
measurement units
Non-SI units
recognized
for use with SI
day: 1 d = 86400 s
hour: 1 h = 3600 s
minute: 1 min = 60 s
liter: 1 l = 10-3 m3
ton: 1 t = 103 kg
degree: 10 = (p/180) rad
minute: 1’ = (p/10800)rad
second: 1” = (p/648000)rad
electronvolt: 1 eV » 1.602177 x 10-19 J
unified atomic mass unit: 1 u » 1.660540 x 10-27 kg
8-30
Units of Measurement Having Special Names
in the International System of Units (SI)
   Time interval (frequency) is the quantity that can be determined with the highest accuracy.  It can be measured with an accuracy greater than 1 part in 1013.  With the help of satellites, it is possible to compare the time scales kept by the national laboratories, worldwide, to an accuracy of ~1 ns.   Time, therefore, plays a central role in metrology and in the definitions of SI units.
   The SI consists of seven base units and a number of derived units, as shown above.  Shown on the next page are the units that do NOT depend on the unit of time.
-------------------------------
R. J. Douglas, et. al, "Frequency Standards, Timekeeping, and Traceable Services at the National Research Council of Canada," Proc. 28th Ann. Precise Time & Time Interval (PTTI) Applications & Planning Meeting, pp. 65-80, 1996.

The chart above, and the one on the next page, were provided by R.J. Douglas, National Research Council Canada, 1997.

E. R. Cohen & B. N. Taylor, “The Fundamental Physical Constants,” Physics Today, pp. BG7-BG14, August 1997.

B. W. Petley, "Time and Frequency Fundamental Metrology," Proceedings of the IEEE, vol. 79, pp. 1070-1076, 1991.