Hydraulic Calculations | Fluid Power | Advanced Fluid Systems

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Hydraulic Pump and Motor Formulas

Pump Flow or Displacement:

GPM (Flow)	=	RPM	X	cu.in. / rev. (Displacement)
		231

Pump Input Horsepower:

HP (Power)	=	PSI (Pressure)	X	GPM (Flow)
HP (Power)	=	1714	X	% (Pump Efficiency)

Torque¹:

lb-in (Torque)	=	PSI (Pressure)	X	cu.in. / rev. (Displacement)
		6.28 (2π)

Torque²:

lb-in. (Torque)	=	HP (Power)	X	63025
		RPM

Cylinder Formulas

Oil Velocity and Pressure Loss Formulas

Thermal Formulas

Centistrokes (Cst) to Saybolt Universal Seconds (SUS, or SSU) Conversion Table

Centistokes (cSt)	Saybolt Universal Seconds (SUS)
1.8	32
2.7	35
4.2	40
5.8	45
7.4	50
8.9	55
10.3	60
11.7	65
13.0	70
14.3	75
15.6	80
16.8	85
18.1	90
19.2	95
20.4	100
22.8	110
25.0	120
27.4	130
29.6	140
31.8	150
34.0	160
36.0	170
38.4	180
40.6	190
42.8	200
47.2	220
51.6	240
55.9	260
60.2	280
64.5	300
69.9	325
75.3	350
80.7	375
86.1	400

Centistokes (cSt)	Saybolt Universal Seconds (SUS)
91.5	425
96.8	450
102.2	475
107.6	500
118.4	550
129.2	600
140.3	650
151	700
162	750
173	800
183	850
194	900
205	950
215	1,000
259	1,200
302	1,400
345	1,600
388	1,800
432	2,000
541	2,500
650	3,000
758	3,500
866	4,000
974	4,500
1,190	5,500
1,300	6,000
1,405	6,500
1,515	7,000
1,625	7,500
1,730	8,000
1,840	8,500
1,950	9,000
2,055	9,500
2,165	10,000

Additional Tools and Reference Materials:

You can find additional tools and conversion software on our Downloads Page. You can also find more information on the formulas and conversions on this page in our Educational Literature page.

Disclaimer:

While fluid power formulas are useful tools for specifying system components and capabilities; other factors such as mechanical efficiencies, fluid dynamics and material limitations must also be considered.

Advanced Fluid Systems has taken great care to verify that the conversions and calculations on this page are correct. However, Advanced Fluid Systems provides no warranties, nor does it assume any legal liability or responsibility for the accuracy, completeness or usefulness of any of the information supplied.

If you have any questions, comments or feedback about the information on this page or our web site, please contact chad.burkhardt@advancedfluidsystems.com

GPM (Flow)	=	The area of your piston in square inches. See the Piston Area formulas above if you do not know the area. in.² (Area)	X	The distance the piston/rod will travel, in inches, for the given time period. in. (Stroke Travel)	X	60
		sec (Time) X 231

Gal (Volume)	=	The area of your piston in square inches. See the Piston Area formulas above if you do not know the area.in² (Piston Area)	X	in. (Stroke)
		231

PSI / ft (Pressure Loss)	=	SSU (Viscosity @ Oper. Temp.)	X	GPM (Flow)
PSI / ft (Pressure Loss)	=	18,300	X	The internal diameter of your pipe in inches.in (I.D. of Pipe)	4

Recommended Maximum Oil Velocity in Hydraulic Lines Pump suction lines - 2 to 4 ft/sec Pressure lines to 500 PSI - 10 to 15 ft/sec Pressure lines to 3000 PSI - 15 to 20 ft/sec Pressure lines over 3000 PSI - 25 ft/sec Oil lines in air/oil system - 4 ft/sec ft / sec (Velocity)	=	GPM (Flow)	X	.3208
	=	The internal diameter of your pipe in inches.in² (I.D. of Pipe)	X	.7854

kWh (Heat)	=	lbs. (Pounds of Material)	X	The specific heat value of the material being heated. Common specific heats include: Water = 1.0 Hydraulic Fluid = .52 Air = .24 Steel = .11 Brass = .092 Nitrogen = .2486 Aluminum = .208 Stainless Steel = .11 Specific Heat	X	(	°F (Beg. Temp.)	-	°F (End Temp.)	)
kWh (Heat)	=	3,413