Calculators will help you to properly size up your pump, piping and fittings. With these tools, you can determine suction loss, friction loss, specific gravity, along with the useful conversion tables.
Head & Pressure Formula
Head in Feet 
= 
(Head in psi) x 2.31
(Sp. Gr.) 
Head in psi 
= 
(Head in feet) x (Sp. Gr.)
2.31 

Net Positive Suction Head
Suction Lift:
NPSH = h_{a} – h_{v} – h_{s} – h_{l}
Flooded suction:
NPSH = h_{a} – h_{v} + h_{s} – h_{l}
h_{a} = the absolute pressure in feed of liquid on the surface of the supply liquid
h_{v} = the vapor pressure of the liquid being pumped expressed in feet of head
h_{s} = the height in feed of the supply liquid surface with respect to the pump inlet
h_{l} = suction line friction losses express in feet of head
These calculations yield the available net positive suction head for a given system.
This must be compared to the required net positive suction head NPSHR calculated
by the manufacturer. NPSH_{A} must exceed NPSH_{R}. 
Affinity Laws
Centrifugal Pumps
For constant speed: 
D_{1}
D_{2} 
= 
Q_{1}
Q_{2} 
= 
√H_{1}
√H_{2} 

BHP_{1} = (D1)^{3}
BHP_{2} = (D2)^{3} 
For constant impeller diameter: 
S_{1}
S_{2} 
= 
Q_{1}
Q_{2} 
= 
√H_{1}
√H_{2} 

BHP_{1} = (S1)^{3}
BHP_{2} = (S2)^{3} 
D = Impeller diameter in inches H = Head in feet
S = Speeds in RPM Q = Capacities in GPM
BHP = Brake Horsepower 
Vacuum Pressure Equivalents:
1 Atmosphere = 29.92 in. Hg = 760mm Hg = 14.7 psi
1 mm Hg = 1 Torr = (3.937x102) in. Hg = 1000µ Hg = 1.333 millibars
1 bar = 103 millibars = 106 microbars = 750.06 mm Hg
1 microbar = 0.75 micron
1 inch Hg = 2.54 x 101 mm Hg
x in. Hg vacuum = (29.92–x) in. Hg absolute
y mm Hg vacuum = (760y) mm Hg absolute
z PSIG = (z + 14.7) PSIA
w PSIA = (w14.7) PSIG 
PUMPING POWER FORMULA
Centrifugal pumps: 
Brake hp 
= 
gpm x H_{ft} x Sp. Gr.
3960 x Efficiency 
Rotary and reciprocating pumps: 
Brake hp 
= 
gpm x psi
1714 x Efficiency 

KW 
= 
pump bhp x 0.7457
motor efficiency 

GENERAL INFORMATION
1 HP = .746 KW or 746 Watts
GPM = Bbls. / Hr. x 0.70
GPM = Bbls. / Day x 0.2917
One Barrel Oil = 42 Gallons 
VISCOSITY
Relationships
Centistokes 
= 
Centipoises
Density 
(usually the same as specific gravity) 
ft^{2} / sec = Centistokes x 1.07639 x 10^{5}
Centistokes = ft^{2} / sec x 92903.4
Approximate Conversions
(50 < SSU ± 100) Centistokes = SSU x 0.226 – 205.3 / SSU
(100 < SSU ≤ 350) Centistokes = SSU x 0.220 – 147.7 / SSU
(SSU > 350 @ 100° F) Centistokes = SSU x 0.21576
(SSU > 350 @ 210° F) Centistokes = SSU x .021426 
FLOW
Lbs. Of Water / Hr x 0.002 = Gal Min.
Gal / Min. x 500 = Lbs of Water / Hr
Lbs of Fluid / Hr
Specific Gravity 
= 
Gal Min. 
Liter Min. x 0.264 = Gal / Min. (US)
GPM x 3.785 = Liters / Min.
Cu. Meters / Hr x 4.4 = Gal / Min. (US)
Gal / Min. x 227 = Cu. Meters / Hr
Kg of Water / Min. x 0.264 = Gal / Min. (US)
Gal Min. x 3.8 = Kg of Water / Min. 
PRESSURE
Ft of Water x 0.433 = PSI
PSI x 2.31 = Ft of Water
Inches Hg. X 0.491 = PSI
Inches Hg. X 1.133 = Ft of Water
ATM x 14.7 = PSI
ATM x 33.9 = Ft of Water
Kg / Sq cm x 14.22 = PSI
Meters of Water x 1.42 = PSI
ATM x 760 = mm Hg.
mm Hg. X 0.39 = Inches Hg.
Bar x 14.5 = PSI
Newton / Meter2 x 1 = Pascal
PSI x 6.9 = kPa (Kilopascal)
kPa x 0.145 =PSI 
VOLUME
Lbs Water x 0.119 = Gal
Gal (Brit) x 1.2 = Gal (US)
Gal x 128 = Fluid Ounces
Cubic Ft x 7.48 = Gal
Cubic in. x 0.00433 = Gal
Gal x 3.785 = Liters
Liter x 0.264 = Gal
Cubic Meters x 264.2 = Gallons
Cubic Meter x 1000 = Liters
Liters x 1000 = Cubic Centimeters
Cubic Centimeters x 0.338 = Fluid Ounces
Fluid Ounces x 29.57 = Cubic Centimeters 
MASS
Gal of Water x 8.336 = Lbs
Cubic Ft of Water x 62.4 = Lbs
Ounces x 0.625 = Lbs
Kilograms x 2.2 = Lbs
Lbs x 0.454 = Kilograms
Metric Ton x 2205 = Lbs 
LENGTH
Mils x 0.001 = Inches
Meters x 3.281 = Feet
Centimeters x 0.394 = Inches
Millimeters x 0.0394 = Inches
Microns x 0.0000394 = Inches 
