pounds per foot-second (lb/(ft-s)) to pound-force-seconds per square foot (lbf-s/ft2) conversion

1 lb/(ft-s) = 0.03108095 lbf-s/ft2lbf-s/ft2 → lb/(ft-s)
Formula
1 lb/(ft-s) = 0.03108095 lbf-s/ft2

Understanding Pounds per foot-second to Pound-force-seconds per square foot Conversion

A pound per foot-second (lb/(ft-s)) uses pound-mass in an absolute-unit viscosity form. A pound-force-second per square foot (lbf-s/ft2), also called the slug per foot-second, is the gravitational US customary viscosity unit consistent with lbf and slug. Converting between them switches viscosity from a mass-based to a force-based US system, differing by the factor of standard gravity (32.174).

Conversion Formula

1 lb/(ft-s)=0.0310809 lbf-s/ft21\ \text{lb/(ft-s)} = 0.0310809\ \text{lbf-s/ft2}

To convert pounds per foot-second to pound-force-seconds per square foot, multiply by this factor:

lbf-s/ft2=lb/(ft-s)×0.0310809\text{lbf-s/ft2} = \text{lb/(ft-s)} \times 0.0310809

Step-by-Step Example

Convert 25 pounds per foot-second to pound-force-seconds per square foot.

lbf-s/ft2=25×0.0310809=0.777024 lbf-s/ft2\text{lbf-s/ft2} = 25 \times 0.0310809 = 0.777024\ \text{lbf-s/ft2}

How to Convert Pounds per foot-second to Pound-force-seconds per square foot

Use the fixed conversion factor to turn any lb/(ft-s) figure into lbf-s/ft2.

  1. Start with your value: Note the measurement in pounds per foot-second (lb/(ft-s)) that you want to convert.
  2. Apply the factor: Multiply that value by 0.0310809, because 1 lb/(ft-s) = 0.0310809 lbf-s/ft2.
  3. Read the result: The product is the equivalent quantity expressed in pound-force-seconds per square foot (lbf-s/ft2).
  4. Worked result: For 25 lb/(ft-s), calculate 25 x 0.0310809 = 0.777024 lbf-s/ft2.

pounds per foot-second to pound-force-seconds per square foot conversion table

pounds per foot-second (lb/(ft-s))pound-force-seconds per square foot (lbf-s/ft2)
00
10.03108095
20.0621619
30.09324285
40.1243238
50.1554048
60.1864857
70.2175667
80.2486476
90.2797286
100.3108095
150.4662143
200.621619
250.7770238
300.9324285
401.243238
501.554048
601.864857
702.175667
802.486476
902.797286
1003.108095
1504.662143
2006.21619
2507.770238
3009.324285
40012.43238
50015.54048
60018.64857
70021.75667
80024.86476
90027.97286
100031.08095
200062.1619
300093.24285
4000124.3238
5000155.4048
10000310.8095
25000777.0238
500001554.048
1000003108.095
2500007770.238
50000015540.48
100000031080.95

What is the pound per foot-second?

The pound per foot-second (lb/(ft·s)) is a unit of dynamic (absolute) viscosity in the English absolute (mass-based) system, where the pound is treated as a unit of mass (pound-mass). It is the FPS analogue of the poise, which is the gram per centimetre-second.

Definition

One pound per foot-second is the viscosity of mass one pound-mass flowing through one foot per second:

1 lb/(ft·s)=1.48816 Pa·s1\ \text{lb/(ft·s)} = 1.48816\ \text{Pa·s}

The exact value comes from 1 lb=0.45359237 kg1\ \text{lb} = 0.45359237\ \text{kg} and 1 ft=0.3048 m1\ \text{ft} = 0.3048\ \text{m}, giving 1 lb/(ft·s)=0.45359237/0.3048=1.4881639 Pa·s1\ \text{lb/(ft·s)} = 0.45359237 / 0.3048 = 1.4881639\ \text{Pa·s}. This is the pound-mass form and must not be confused with the gravitational pound-force-second per square foot, which is about 32.174 times larger.

Origin and History

This unit arises from the English absolute (or "poundal") system of mechanics, in which mass is the base quantity and force is the derived poundal. It appears in older engineering and chemical-engineering literature, particularly British texts, as a direct mass-based counterpart to the CGS poise.

Law and Notable Facts

It is not an SI unit. A useful relationship: 1 lb/(ft·s)=1,488.16 cP1\ \text{lb/(ft·s)} = 1{,}488.16\ \text{cP}, and the difference between this mass-based unit and the force-based lbf·s/ft² is exactly the standard gravitational conversion factor gc=32.17405g_c = 32.17405 (the ratio of pound-force to poundal).

Real-World Examples and Conversions

Water at 20 °C (0.001002 Pa·s0.001002\ \text{Pa·s}) is about 6.73×10−4 lb/(ft·s)6.73\times10^{-4}\ \text{lb/(ft·s)}. A fluid of 1 lb/(ft·s)=1.48816 Pa·s=1,488 cP1\ \text{lb/(ft·s)} = 1.48816\ \text{Pa·s} = 1{,}488\ \text{cP} is roughly as viscous as light honey. Motor oil around 0.2 Pa·s0.2\ \text{Pa·s} is about 0.134 lb/(ft·s)0.134\ \text{lb/(ft·s)}.

What is the pound-force-second per square foot?

The pound-force-second per square foot (lbf·s/ft²) is the unit of dynamic (absolute) viscosity in the English/US customary gravitational system. It is sometimes called the "slug per foot-second" because it is numerically identical to that combination.

Definition

One pound-force-second per square foot is the viscosity that produces a shear stress of one pound-force per square foot at a shear rate of one per second:

1 lbf·s/ft2=47.8803 Pa·s1\ \text{lbf·s/ft}^2 = 47.8803\ \text{Pa·s}

The exact value follows from the definitions 1 lbf=4.4482216152605 N1\ \text{lbf} = 4.4482216152605\ \text{N} and 1 ft=0.3048 m1\ \text{ft} = 0.3048\ \text{m}, giving 1 lbf·s/ft2=4.4482216152605/0.30482=47.880259 Pa·s1\ \text{lbf·s/ft}^2 = 4.4482216152605 / 0.3048² = 47.880259\ \text{Pa·s} exactly. It equals one reyn's cousin in ft units, and is identical to 1 slug ft−1 s−11\ \text{slug}\,\text{ft}^{-1}\,\text{s}^{-1}.

Origin and History

The unit belongs to the foot-pound-second (FPS) gravitational system used by English-speaking engineers, in which force (the pound-force) rather than mass is a base concept. It became standard in aeronautical and mechanical engineering texts in the United States during the 20th century, where fluid properties were often tabulated in customary units.

Law and Notable Facts

It is not an SI unit; the SI equivalent is the pascal-second. A closely related unit, the reyn (1 lbf·s/in²), is used in lubrication engineering and equals 6.89476×103 Pa·s6.89476\times10^{3}\ \text{Pa·s}, exactly 144 times the lbf·s/ft² because there are 144 square inches per square foot.

Real-World Examples and Conversions

Water at 20 °C, about 1.002 cP=0.001002 Pa·s1.002\ \text{cP} = 0.001002\ \text{Pa·s}, is roughly 2.09×10−5 lbf·s/ft22.09\times10^{-5}\ \text{lbf·s/ft}^2. Conversely, 1 lbf·s/ft2=47.8803 Pa·s=47,880.3 cP1\ \text{lbf·s/ft}^2 = 47.8803\ \text{Pa·s} = 47{,}880.3\ \text{cP}, a very viscous fluid comparable to thick syrup. Air at room temperature (≈1.8×10−5 Pa·s\approx 1.8\times10^{-5}\ \text{Pa·s}) is about 3.8×10−7 lbf·s/ft23.8\times10^{-7}\ \text{lbf·s/ft}^2.

Frequently Asked Questions

What is the formula to convert pounds per foot-second to pound-force-seconds per square foot?

Multiply the value in lb/(ft-s) by 0.0310809 to get lbf-s/ft2. For example, 25 lb/(ft-s) equal 0.777024 lbf-s/ft2.

How many pound-force-seconds per square foot are in one pound per foot-second?

There are 0.0310809 lbf-s/ft2 in a single lb/(ft-s), so the value in lbf-s/ft2 is always smaller when the factor is less than one.

How do I convert pound-force-seconds per square foot back to pounds per foot-second?

Reverse the operation by multiplying lbf-s/ft2 by 32.1741, since 1 lbf-s/ft2 = 32.1741 lb/(ft-s).

What does 100 pounds per foot-second equal in pound-force-seconds per square foot?

Multiplying gives 100 x 0.0310809 = 3.1081 lbf-s/ft2.

When is this lb/(ft-s) to lbf-s/ft2 conversion used?

Converting between them switches viscosity from a mass-based to a force-based US system, differing by the factor of standard gravity (32.174).

People also convert

lb/(ft-s) to Pa-slb/(ft-s) to mPa-slb/(ft-s) to Plb/(ft-s) to cP

Complete pounds per foot-second conversion table

lb/(ft-s)
UnitResult
pascal-seconds (Pa-s)1.488164 Pa-s
millipascal-seconds (mPa-s)1488.164 mPa-s
poises (P)14.88164 P
centipoises (cP)1488.164 cP
pound-force-seconds per square foot (lbf-s/ft2)0.03108095 lbf-s/ft2

Dynamic viscosity conversions