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The Metric System, Abbreviations, and Conversions
for Common Units of Measure
[ Table
of Contents ]
 Rules for Use
of Abbreviations  The Metric System

 Length and Distance  Volume
 Liquid Volumes  Mass
 Area  Temperature
 Pressure 
 Humidity  Concentration
 Salinity  pH
 Time 
This page presents the most common abbreviations you will
use in general biology, especially those for units of measure.
General Rules for Abbreviating Units
of Measure
 Always abbreviate units when reporting numerical information.
 Unless otherwise noted, singular and plural
units are abbreviated the same.
 Percent is not abbreviated, but is represented by
the familiar "%" symbol.
 Always put a space between the number and unit,
e.g., 203.65 m, 457 um
 pH: The
proper method for reporting pH is to place the unit before the
number (pH 7); never insert the word "of" between the
unit and number and avoid splitting the unit and number within
a sentence  they should always go together.
 When do you abbreviate units vs. spelling out
the unit(s) as word(s)?
 abbreviate units when you are reporting a numerical
value:
"The maximum depth achieved by
the ROV was 124 m approximately
2.3 km due
south of Pt. Lobos."
 spell out the unit as a word when using it in a nonnumerical
context, e.g.,
"All measurements were made in
millimeters
unless otherwise indicated."
 When starting a sentence with a number and unit, both must
be spelled out as words (this is something to avoid, if possible),
e.g.,
"One
thousand six hundred and eightyseven kilograms
of ground beef were randomly sampled and tested for E.coli
contaminants between 21 August and 21 November, 1995."
The Metric System
The Metric System of measurement is the standard used by most
scientific disciplines. The system is based upon measures of
distance (in meters), volume (in liters), and mass (in grams).
Scales of measurements increase or decrease as multiples of ten
which facilitates expression of measurement values using the
decimal system. The table below shows the most common prefixes
and their relative magnitudes. Note that
web browsers do not support use of superscripts and subscripts
very well, so the notation 10^2
means "10 to the power of 2,
or 10 squared". Similarly, the notation 102 should
be read as "10 to the power of 2".
Prefix 
Scientific Notation 
Decimal equivalents 
Example Units 
kilo (k) 
= 10^3 
= 1000 
kilogram (kg);
kilometer (km) 
centi (c) 
= 102 
= 0.01 
centimeter (cm) 
milli (m) 
= 103 
= 0.001 
milligram (mg);
millimeter (mm) 
micro (u) 
= 106 
= 0.000001 
microgram (ug)
microliter (uL) 
nano (n) 
= 109 
= 0.000000001 
nanogram (ng)
nanoamperes (nA) 
pico (p) 
= 1012 
= 0.000000000001 
picogram (pg)
picoamperes (pA) 
Conversions
Units of Distance and Length 
Metric Equivalents
1 km = 1000 m; 1 m = 100 cm = 1000 mm = 10^6
um = 10^9 nm

Metric Unit 
multiplied by 
= English Unit 
millimeters
centimeters
centimeters
meters
meters
meters
kilometers
kilometers 
0.0394
0.394
0.0328
39.4
3.28
1.1
3,281
0.621 
inches (in)
inches
feet (ft)
inches
feet
yards (yd)
feet
miles (mi) 
English Equivalents
1 mi = 1,760 yd = 5,281 ft; 1 yd = 3 ft = 36 in

English Unit 
multiplied
by 
= Metric Unit 
inches (in)
inches
inches
feet (ft)
yards (yd)
yards
miles (mi) 
25.4
2.54
0.254
30.48
91.44
0.9144
1.609 
millimeters
centimeters
meters
centimeters
centimeters
meters
kilometers 
Top of Page
Units of Mass
Metric Equivalents
1 mt (metric ton) = 1000 kg = 2,205 lb
1 kg = 1000 g = 2.205 lb = 35.2802 oz
1 g = 1000 mg = 10^6 ng = 10^9
pg

Metric Unit 
Multiplied by 
= English Unit 
gram (g) 
0.035 
ounces (oz) 
kilogram (kg) 
2.2 
pounds (lb) 
metric ton (mt) 
1.102 
ton (t) 
English Equivalents
1 ton = 2000 lb = 907.2 kg or 0.9072 mt
1 lb = 16 oz = 0.4536 kg = 453.6 g

English Unit 
Multiplied by 
= Metric Unit 
ounce (oz) 
28 
grams (g) 
pound (lb) 
0.4536 
kilograms (kg) 
tons (t) 
0.9072 
metric tons (mt) 
Top of Page
Units of Volume
Metric Equivalents
1 cm^3 (or cc) = 1000 mm^3
= 0.061 in^3
1 m^3 = 10^6 cm^3 = 61,024 in^3 = 35.31
ft^3 = 1.308 yd^3

Metric Unit 
Multiplied by 
= English Unit 
cubic centimeters (cm^3) 
0.061 
cubic inches (in^3) 
cubic meters (m^3) 
35.31 
cubic feet (ft^3) 
cubic meters 
1.308 
cubic yards (yd^3) 
English Equivalents
1 ft^3 = 1,728 in^3
= 28,317 cm^3 = 0.02832 m^3
1 yd^3 = 27 ft^3
= 0.7646 m^3

English Unit 
Multiplied by 
= Metric Unit 
cubic inches 
16.393 
cubic centimeters 
cubic feet 
0.03 
cubic meters 
cubic yards 
0.76 
cubic meters 
Top of Page
Units of Liquid Volumes
Metric Equivalents
1 L = 1000 ml = 2.113 pt (pints) = 1.06 qt (quarts)
= 0.264 US gal
1 ml (or cm^3) = 1000 ul = 0.03 fl oz
(fluid ounces)

Metric Unit 
Multiplied by 
= English Unit 
milliliters (ml) 
0.02957 
fluid ounces (fl oz) 
liters (L) 
2.13 
pints (pt) 
liters (L) 
1.0567 
quarts (qt) 
English Equivalents
1 US gal = 4 qt = 8 pt = 128 fl oz = 3.785 L
1 qt = 2 pt = 32 fl oz = 946.4 ml or 0.9464 L
1 pt = 16 fl oz = 473.2 ml or 0.213 L
1 fl oz = 29.57 ml

English Unit 
Multiplied by 
= Metric Unit 
teaspoons (tsp) 
5 
milliliters (ml) 
tablespoons (tbsp) 
15 
milliliters 
fluid ounces (fl oz) 
29.57 
milliliters 
cups (c) 
0.24 
liters (L) 
pints (pt) 
0.4732 
liters 
quarts (qt) 
0.9464 
liters 
US gallons (US gal) 
3.785 
liters 
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Units of Area
Metric Equivalents
1 km^2 = 100 ha = 1,000,000 m^2 = 270 A (acres) =
0.3861 mi^2
1 ha (hectare) = 10,000 m^2 = 107,600 ft^2 = 2.471 A
1 m^2 = 10,000 cm^2 = 1,000,000 mm^2 = 1,550 in^2 = 1.196 yd^2
1 cm^2 = 100 mm^2 = 0.155 in^2
1 mm^2 = 1,000,000 um^2

Metric Unit 
Multiplied by 
= English Unit 
centimeters squared 
0.155 
inches squared 
meters squared 
1.196 
yards squared 
kilometers squared 
0.3861 
miles squared 
English Equivalents
1 mi^2 = 640 A = 27,878,400 ft^2 = 259 ha = 2.59 km^2
1 A = 4,840 yd^2 = 43,560 ft^2 = 4,407 m^2 = 0.405 ha
1 yd^2 = 9 ft^2 = 1296 in^2 = 8,361 cm^2 = 0.836 m^2
1 ft^2 = 144 in^2 = 929 cm^2
1 in^2 = 6.452 cm^2

English Unit 
Multiplied by 
= Metric Unit 
inches squared 
6.452 
centimeters squared 
feet squared 
0.0929 
meters squared 
yards squared 
0.836 
meters squared 
acres (A) 
0.405 
hectares (ha) 
miles squared 
2.59 
kilometers squared 
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Units of Temperature
Temperature Equivalents
K = Kelvin  C = Celsius 
F = Fahrenheit
0 K = 273.15 C = absolute zero (no molecular motion)
273.15 K = 0 C = 32 F = freezing point of water/ melting point
of ice
373.15 K = 100 C = 212 F = boiling point of water

Fahrenheit (F) to Celsius (C) Conversion
(degrees F  32)
x 5/9 = degrees C

Celsius (C) to Fahrenheit (F) Conversion
(degrees C x 9/5
) + 32 = degrees F



Top of Page
Units of Pressure
 OnLine
Unit Converter
Top of Page
Units of Humidity
Top of Page
Units of Concentration
Concentration usually refers to a mass/volume relationship.
Percent (%) 
= grams solute / 100 ml
solvent;
To convert to molar concentration multiply grams by 10, then
divide by the formula weight (FW) of the solute. 
Molarity (M) 
= moles solute per liter of solvent
For example,
1 M = 1 mole/liter; where,
1 mole = 6.023 x 10^23 molecules
= 1 molecular weight (MW)
~ 1 formula weight (FW)
Molarity may also be expressed as mM (millimolar), where 1 mM
equals 103 M, when working with low concentrations.

Salinity

= grams total solutes per kg of seawater
Salinity is usually expressed as "parts per thousand"
= ppt.
Coastal seawater has approximately 3032 g solutes per kg = 3032
ppt salinity.

Units of pH
In contrast to other units, report pH with the unit before
the number: e.g., pH 8.2. When reporting
a series of pH values, report the unit only at the beginning:
e.g., ...buffered to pH 3, 5, 7, and 9....
Units of Time
The most frequent units time used in
the biological sciences are:
Years 
yr 
Days 
d 
Hours 
h 
Minutes 
min 
Seconds 
sec or s 
Milliseconds 
msec 
Modified 32608
Department of Biology, Bates
College, Lewiston, ME 04240
