Appendix E - Units of Measure and Conversion Factors

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USER'S GUIDE

This section presents definitions, physical constants and conversion factors that are used in the text and may be useful as reference data. Scroll down through the list or use the alphabetical links below to go directly to the section where your word or symbol is located.

A

ATMOSPHERE (atm):

The pressure exerted by 76 cm mercury with a density of 13.5951 gm/cm³ at 1g (the standard barometric pressure at sea level).

1 atm = 325 x 10⁶ dynes/cm²

1 atm = 1033.2 gm/cm²

1 atm = 760 mm Hg

1 atm = 14.696 psi

1 atm = 101.329 kPa (kilo Pascals)

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B

BRITISH THERMAL UNIT (Btu):

1 Btu = 1.0559 x 10¹⁰ ergs

1 Btu = 1055.9 joules

1 Btu = 251.995 gm-cal

1 Btu = 778.77 ft-lbs

1 Btu = 0.25199 kcal

1 Btu/hr = 0.1667 Btu/min

1 Btu/hr = 0.04199 kcal/min

1 Btu/hr = 0.2932 watt

1 Btu/min = 0.25199 kcal\min

1 Btu/min = 0.23599 hp

1 Btu/min = 17.595 watts

1 Btu/ft², hr = 2.7125 kcal/m² hr

Btu/hr to joules:

1 Btu/hr = 1.05435 x 10³ joule/hr

800 Btu/hr x 1054.35 = 843480 joule/hr

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C

CANDELA (cd):

1 cd = 1.018 candle

CANDLE (c):

The unit of luminous intensity.

1 c = 1 lumen/steradian

CELSIUS (°C):

(See Degrees Centigrade)

CENTIGRADE (°C):

(See Degrees Centigrade)

CENTIMETER (cm):

1 cm = 0.03280 ft

1 cm = 0.3937 in

1 cm = 0.01 m

1 cm = 10mm

1 cm = 1x10⁴m (micron)

CENTIMETER-CANDLE (phot):

1 phot = 1 x 10⁴ lux

CENTIMETERS PER SECOND PER SECOND:

1 cm/sec² = 0.0328 ft/sec²

CLO (clo):

The unit of insulation resistance for clothing.

1 clo = 0.18°C m²hr/kcal

1 clo = 0.88°F ft²hr/Btu

CUBIC CENTIMETER (cc or cm³):

1 CC = 3.531 x 10^-5 ft³

1 CC = 0.061023 in³

1 CC = 1 x 10-6 m³

1 CC = 1000 mm³

1 CC = 2.6417 x 10^-4 gal (US fluid)

1 CC = 0.0338 oz (US fluid)

1 CC = 2.113 x 10^-3 pint (US fluid)

1 cc/sec = 0.0021186 ft3/min

CUBIC FOOT

1 ft³= 1728 in³

1 ft³= 28.32 liters

1 ft³= 0.02832 m³

1 ft³/min = 472.0 cc/sec

1 ft³/min = 0.4720 liter/sec

1 ft³/min = 62.43 lbs H₂O/min

1 ft³/sec = 1699.3 liters/min

CUBIC INCH:

1 in³ = 5.787 x 10^-4 ft³

1 in³ = 1.639 x 10² liter

1 in³ = 1.639 x 10^-5 m³

CUBIC METER:

1 m³= 35.3144 ft³

1 m³= 6.1023 x 104 in³

1 m³= 999.973 liters

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D

DECIBEL (db):

Used for comparing power levels, acoustical or electrical. (See also Sound Pressure Level).

1 db = 10 log₁₀ P/PO

where P is the power to be compared to a reference power PO

1 db = 1 bel is equal to an increase in power (P) by a factor of 10

DEGREE (ANGULAR) (deg):

1 deg = 60 minutes

1 deg = 0.01745 radian

1 deg = 3600 seconds

1 deg = 1.7453 X 10^-2 steradian --- note, this is changed from the original version that contains an error

DEGREES TO RADIANS:

1 deg = π/180 rad

60° x π/180 = 1.0472 = 1 rad

DEGREES CENTIGRADE (°C):

°C = 5/9 * (°F - 32)

DEGREES FAHRENHEIT (°F):

°F = (9/5 * °C) + 32

DEGREES PER SECOND:

1 deg/sec = 0.017453 radian/sec

1 deg/sec = 0.1667 rpm

DYNE (dyne):

1 dyne = 1.0197 x 10^-6 kg

1 dyne = 2.2481 x 10^-6 lb

1 dyne-cm = 1 erg

DYNE PER SQUARE CENTIMETER

1 dyne/cm² = 9.8692 x 10^-7 atm

1 dyne/cm²= 0.0010197 gm/cm²

1 dyne/cm²= 4.0148 x 10^-4 in H₂O

1 dyne/cm²= 7.5006 x 10^-4 mm Hg

1 dyne/cm²= 1.4504 x 10^-5 psi

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E

ERG (erg):

1 erg = 9.4805 x 10^-11 Btu

1 erg = 7.3756 x 10^-8 ft-lb

1 erg = 2.3889 x 10^-11 kcal

1 erg = 8.8510 x 10^-7 lb-in

1 erg = 1 dyne-cm

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F

FAHRENHEIT (°F):

(See Degrees Fahrenheit).

FOOT (ft):

(See also Square Foot, Cubic Foot).

1 ft = 30.48 cm

1 ft = 12 in

1 ft = 0.3048 m

FOOT-CANDLE (fc):

1 ft-c = 1 lumen/ft²

1 ft-c = 10.764 lumen/m²

1 ft-c = 10.75 lux

FOOT-LAMBERT (ft-L):

1 ft-L = 1.0764 millilamberts

1 ft-L = 0.32 decibels with respect to 1 mL

FOOT PER MINUTE

1 ft/min = 0.3048 m/min

1 ft/min = 0.005080 m/sec

1 ft/min = 0.011364 mph

FOOT PER SECOND:

1 ft/sec = 1.0973 km/hr

1 ft/sec = 0.5921 knot

1 ft/sec = 0.6818 mph

FOOT-POUND (ft-lb):

1 ft-lb = 0.001285 Btu

1 ft-lb = 1.3558 x 10⁷ ergs

1 ft-lb = 3.2389 x 10^-4 kcal

1 ft-lb/min = 3.0303 x 10^-5 hp

1 ft-lb/min = 0.01667 ft-lb/sec

1 ft-lb/min = 0.022597 watt

1 ft-lb/sec = 0.001818 hp

1 ft-lb/sec = 0.01943 kcal/min

1 ft-lb/sec = 1.3558 watts

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G

G (g):

The acceleration of gravity (also the acceleration of a vehicle).

1g = 9.81 m/s²

1 ft/sec = 1.0973 km/hr

1 ft/sec = 0.5921 knot

1 ft/sec = 0.6818 mph

GRAM (gm):

1 gm = 0.001 kg

1 gm = 1000 mg

1 gm = 0.03527 oz

1 gm = 0.0022046 lb

1 gm/cm³ = 62.428 lbs/ft³

1 gm/hr = 0.540 lb/day

1 gm/hr = 0.0003757 lb/min

1 gm/liter = 0.062427 lb/ft³

1 gm/cm² = 9.6784 x 10^-4 atm

1 gm/cm² = 980.665 dynes/cm²

1 gm/cm² = 0.9356 mm Hg

1 gm/cm² = 0.014223 psi

1 gm/m²/hr = 2.78 x 10^-5 gm/cm²/sec

1 gm/m²/hr = 0.7448 lb/ft²/hr

GRAM-CALORIE (gm-cal):

1 gm-cal = 30874 ft-lbs

1 gm-cal = 0.001 kcal

GRAY (Gy):

The International System of Units (SI) unit for the amount of ionizing radiation energy absorbed by tissue.

1 Gy = 100 rads

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H

HORSEPOWER (hp):

1 hp = 3.300 x 10⁴ ft-lbs/min

1 hp = 550 ft-lbs/sec

1 hp = 10.688 kcal/min

1 hp = 745.7 watts

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I

INCH (in):

(See also Cubic Inch, Square Inch)

1 in = 2.540 cm

1 in = 0.0833 ft

1 in = 25.40 mm

INCH OF WATER (in H₂O):

1 in H₂O (at 4°C) = 0.002458 atm

1 in H₂O (at 4°C) = 2490.82 dynes/cm²

1 in H₂O (at 4°C) = 0.0361 psi

1 in H₂O (at 4°C) = 1.868 mm Hg

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J

JOULE (joule):

1 joule = 1 watt-sec

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K

KILOGRAM (kg):

1 kg = 1000 gm

1 kg = 2.205 lb

1 kg = 35.28 oz

KILOGRAM-CALORIE (kcal or large Calorie):

1 kcal = 3.9683 Btu

1 kcal = 4.186 x 10¹⁰ ergs

1 kcal = 1000 gm-cal

1 kcal = 3087 ft-lbs

1 kcal/hr = 0.0661 Btu/min

1 kcal/hr = 0.857 ft-lbs/sec

1 kcal/hr = 0.1667 kcal/min

1 kcal/hr = 1.161 watts

1 kcal/m²hr = 0.3687 Btu/ft²hr

1 kcal/min = 3.9685 Btu/min

1 kcal/min = 51.457 ft-lbs/sec

1 kcal/min = 0.093557 hp

1 kcal/min = 69.767 watts

KILOGRAM-CENTIMETER SQUARED:

1 kg-cm² = 0.3417 lb-in²

KILOGRAM-METER PER SECOND:

1 kg-m/sec = 7.2330 ft-lb/sec

1 kg-m/sec = 9.80665 watts

KILOMETER (km):

1 km = 105 cm

1 km = 3281 ft

1 km = 103 meters, m

1 km = 0.6214 statute miles, mi

1 km = 0.54 nautical miles, nm

KILOPASCAL:

1kPa = 6.895 psi

1kPa = 4.754 x 10⁵ dynes/cm²

1 psi = 0.145 kPa

KILOMETERS PER HOUR:

1 km/hr = 0.9113 ft/sec

1 km/hr = 0.5396 knot

1 km/hr = 0.6214 mph

KNOT (nautical mile per hour):

1 knot = 1.689 ft/sec

1 knot = 1.853 km/hr

1 knot = 1.1516 mph

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L

LAMBERT (L): Unit of surface brightness.

1L = 0.3183 c/cm²

1L = 2.0536 c/in²

1L = 1 lumen/cm²

LITER (l):

1 liter = 0.03531 ft³

1 liter = 61.02 in³

1 liter = 1000 ml

1 liter/min = 5.886 x 10^-4 ft³/sec

1 liter/sec = 2.12 ft³/min

LUMEN (lumen):

1 lumen = 0.001496 watt

1 lumen = 0.07958 spherical candle power

1 lumen/ft²= 1 ft-c

1 lumen/ft²= 10.764 lumen/m²

LUMENS PER SQ. METER TO FT CANDLES:

1 lumen/m²= 0.0929 ft. candle

LUX:

1 lux = 0.093 ft-c (see meter-candle)

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M

METER (m):

(See also Cubic Meter).

1m = 100 cm

1m = 3.281 ft

1m = 39.37 in

METER-CANDLE (lux):

1 lux = 1 lumen/m²

1 lux = 0.092903 ft-c

METER PER SECOND (m/sec):

1 m/sec = 3.281 ft/sec

1 m/sec = 3.600 km/hr

1 m/sec = 2.2369 mph

MICRON (μ or mu):

A unit of length equal to one-millionth of a meter or one-thousandth of a millimeter, usually called micrometer.

1 μ = 10^-6 meter

1 μ = 3.937 x 10^-5 in

1 μ = 0.001 mm

MIL (mil):

1 mil = 0.001 in

1 mil = 0.0254 mm

1 mil = 25.40μ (microns)

MILES (statute) (mi):

1 mi = 1,609 x 10⁵ cm

1 mi = 5,280 ft

1 mi = 1.609 km

MILES PER HOUR (mph)

1 mph = 88 ft/min

1 mph = 1.4667 ft/sec

1 mph = 1.6093 km/hr

1 mph = 0.8684 knot

MILLIGRAM (mg):

1 mg = 0.001 gm

1 mg = 3.5274 x 10^-5 oz

1 mg = 2.2046 x 10^-6 lb

1 mg/m³= 6.243 x 10^-4 lb/ft³

MILLILAMBERT (ml):

(perfectly diffused light)

1 mL = 0.929 lumen/ft²

MILLILITER (ml):

1 ml = 1.000028 cc

1 ml = 0.061025 in³

1 ml = 0.001 liter

1 ml = 0.0338 oz (US fluid)

MILLILITERS PER HOUR:

1 ml/hr = 0.06102 in³/hr

MILLIMETER(mm):

(See also Square Millimeter)

1mm = 0.10 cm

1mm = 0.03937 in

1mm = 1000 μ

MILLIMETER OF MERCURY (mm Hg):

1mm Hg (at 0°C) = 0.0013158 atm

1mm Hg (at 0°C) = 1333.22 dyne/cm²

1mm Hg (at 0°C) = 1.3595 gm/cm²

1mm Hg (at 0°C) = 0.019337 psi

1mm Hg (at 0°C) = 0.535 in H₂O

1mm Hg (at 0°C) = 0.1333 kPa

MILLISECONDS (msec):

1 msec = 0.001 sec

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N

NAUTICAL MILES (nm):

1 nm = 0.87 statute miles

1 nm = 1.85 kilometers

NEWTONS TO POUNDS:

1 N = 0.22507 lbf

NEWTON CENTIMETERS TO INCH OUNCES:

1 N-cm = 1/.706 in oz

70N-cm x 1/.706 = 99.15 = 100 in oz

NEWTON METERS TO FOOT POUNDS:

1Nm = 1/1.356 ft lb

15Nm x 1/1.356 = 11.06 = 11 ft lb

NEWTON METERS TO INCH POUNDS:

1 Nm = 1/.11298 in lb

4 Nm x 1/.11298 = 35.4 = 3 5 in lb

NIT:

Unit of luminance equal to the luminance provided by one candle of radiant flux emitted per square meter of surface - candela per square meter (Cd m²).

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O

OUNCE (oz):

1 oz = 28.3495 gm

1 oz = 0.0625 lb

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P

PASCALS (Pa)

Pa = 4.75389 dynes/cm²

Pa = 6.895 x 10^-3 psi

PARTS PER MILLION (ppm).

1 ppm = 1.0 mg/liter of H₂O

1 ppm = 8.345 lbs/million gallons

PHON (phon):

1 phon unit = SPL of a 1000 cycle/sec tone

PHOT:

(See Centimeter Candle)

Physical Constants:

Acceleration of gravity (g)

= 32.17 ft/sec²= 980.6 cm/sec²

Avogradro's number (N)

= 6.0221367 x 10²³ molecules/gram-mole

Density of air at 0°C and 760 mm Hg

= 0.0012929 grams/cm³(0.0807 lb/ft³)

Density of water at 0°C

= .099984 grams/cm³

Heat of fusion of water at 1.0 atm

= 79.7 calories/gram = 144 Btu/pound

Heat of vaporization of water at 1.0 atm

= 540 calories/gram = 970 Btu/pound

Naperian-logarithm base

= 2.71828183

Pi (π)

= 3.14159265

Specific heat of air

= Cp = 0.238 cal/gram (°C)

Velocity of light (c)

= 2.99792458 x 10¹⁰ cm/sec

Velocity of sound in dry air at 0°C, 1 atm

= 33,136 cm/sec = 1,089 feet/sec

POISE: Unit of viscosity.

1 poise = 1 dyne/sec, cm²

1 poise = 1 gm/cm, sec

1 poise = 0.067196 lb/ft, sec

POUND (lb):

1 lb = 453.5924 gm

1 lb = 0.45359 kg

1 lb = 16 oz

1 lb = 4.448 N

1 lb/day = 18.89 gm/hr

1 lb/hr = 0.7559 gm/min

1 lb/hr = 10.886 kg/day

POUND-INCH (lb-in):

1 lb-in = 1.1298 x 10⁶ dyne/cm

POUND-INCH SQUARED:

Unit of moment of inertia

1 lb-in²= 2.9264 kg-cm²

POUND OF WATER PER MINUTE (lb H₂O/min):

1 lb H₂O/min = 0.01603 ft³/min

1 lb H₂O/min = 2.670 x 10-4 ft³/sec

POUND PER CUBIC FOOT (lb/ft³):

1 lb/ ft³= 0.01602 gm/ cm³

POUNDS PER SQUARE INCH (psi):

1 psi = 0.06805 atm

1 psi = 6.8947 x 10⁴ dyne/cm²

1 psi = 70.307 gm/cm²

1 psi = 51.715 mmHg

1 psi = 27.7 in H₂O

1 psi = 145.03 Pa

POUNDS PER SQUARE INCH ABSOLUTE (psia):

Absolute pressure, where 0 psia = vacuum

1 psia = 0.1449 kpascals

POUND WEIGHT (1 wt):

1 lb wt = 4.4482 x 10⁵ dynes

1 lb wt = 453.59 gm wt

1 lb wt = 16 oz

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Q

none

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R

RAD (rad):

Radiation absorbed dose.

1 rad = 100 ergs/gm of irradiated material

RADIAN (rad):

1 radian = ½π circumference revolution (0.15915)

1 radian = 57.296 deg

1 radian/sec = 57.296 deg/sec

1 radian/sec = 9.549 rpm

1 radian/sec² = 572.96 rpm²

REVOLUTIONS PER MINUTE (rpm):

1 rpm = 6 deg/sec

1 rpm = 0.10472 radian/sec

1 rpm² = 0.001745 radian/sec²

ROENTGEN (r):

1 r = ionization by x-rays or gamma-rays producing 1 electrostatic unit of charge in 1 cm³ of air (STP)

1 r = 83.0 ergs/gm

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S

SIEVERT (Sv):

Sv is the International System of Units (SI) unit for ionizing radiation dose equivalent. (Refer to Figure 5.7.2.1.3.1-1 for definition of Q values)

1 Sv = 100 rem = (Gy) (Q)

SOUND PRESSURE LEVEL (SPL):

SPL is sound pressure related logarithmically to a reference level of pressure (P_o), which by convention is 0.0002 dynes/cm². The defining equation is:

SPL = 20 log₁₀ P/PO in decibels

SQUARE CENTIMETER (cm2):

1 cm²= 1.076 x 10^-3 ft²

1 cm²= 0.1550 in²

1 cm²= 100 mm²

SQUARE FOOT (ft²):

1 ft² = 929.0304 cm²

1 ft² = 144 in²

SQUARE INCH (in²):

1 in² = 6.4516 cm²

1 in²= 0.006944 ft²

1 in²= 645.1626 mm²

SQUARE MILLIMETER (mm²):

1 mm² = 0.01 cm²

1 mm²= 0.001550 in²

STERADIAN:

The solid angle which encloses a surface on a sphere equal to the square of the radius.

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