Understanding pound-force-seconds per square foot to centipoises Conversion
The pound-force-second per square foot (lbf·s/ft²) is the US/British Gravitational unit of dynamic viscosity, a large unit equal to about 47,880 centipoise. The centipoise (cP) is one-hundredth of a poise and the everyday CGS-based viscosity unit, with water near 1 cP. This conversion turns imperial gravitational viscosity values into the centipoise readings used across coatings, lubricants, and lab work.
Conversion Formula
To convert pound-force-seconds per square foot to centipoises, multiply by this factor:
Step-by-Step Example
Convert 25 pound-force-seconds per square foot to centipoises.
How to Convert pound-force-seconds per square foot to centipoises
Convert an imperial gravitational viscosity into everyday centipoise.
- Take the lbf·s/ft² value: Record the dynamic viscosity in imperial units.
- Multiply by 47,880.26: This is the number of centipoise in one lbf·s/ft².
- Report in centipoise: The product is the viscosity in cP.
- Worked result: 25 lbf·s/ft² × 47,880.26 = 1,197,007 cP.
pound-force-seconds per square foot to centipoises conversion table
| pound-force-seconds per square foot (lbf-s/ft2) | centipoises (cP) |
|---|---|
| 0 | 0 |
| 1 | 47880.26 |
| 2 | 95760.52 |
| 3 | 143640.8 |
| 4 | 191521 |
| 5 | 239401.3 |
| 6 | 287281.6 |
| 7 | 335161.8 |
| 8 | 383042.1 |
| 9 | 430922.3 |
| 10 | 478802.6 |
| 15 | 718203.9 |
| 20 | 957605.2 |
| 25 | 1197006 |
| 30 | 1436408 |
| 40 | 1915210 |
| 50 | 2394013 |
| 60 | 2872816 |
| 70 | 3351618 |
| 80 | 3830421 |
| 90 | 4309223 |
| 100 | 4788026 |
| 150 | 7182039 |
| 200 | 9576052 |
| 250 | 11970060 |
| 300 | 14364080 |
| 400 | 19152100 |
| 500 | 23940130 |
| 600 | 28728160 |
| 700 | 33516180 |
| 800 | 38304210 |
| 900 | 43092230 |
| 1000 | 47880260 |
| 2000 | 95760520 |
| 3000 | 143640800 |
| 4000 | 191521000 |
| 5000 | 239401300 |
| 10000 | 478802600 |
| 25000 | 1197006000 |
| 50000 | 2394013000 |
| 100000 | 4788026000 |
| 250000 | 11970060000 |
| 500000 | 23940130000 |
| 1000000 | 47880260000 |
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:
The exact value follows from the definitions and , giving exactly. It equals one reyn's cousin in ft units, and is identical to .
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 , 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 , is roughly . Conversely, , a very viscous fluid comparable to thick syrup. Air at room temperature () is about .
What is the centipoise?
The centipoise (cP) is a CGS unit of dynamic (absolute) viscosity, equal to one hundredth of a poise. It is the most widely used practical viscosity unit in industry because water at about 20 °C has a viscosity of very nearly 1 cP.
Definition
One centipoise equals one hundredth of a poise, which in SI units is exactly one millipascal-second:
Since (the poise being defined as ), the centipoise is of that, i.e. exactly. The unit is dimensionally mass per length per time.
Origin and History
The poise is named after the French physician and physiologist Jean Léonard Marie Poiseuille (1797–1869), who studied the flow of liquids (blood) through narrow tubes and formulated what became the Hagen–Poiseuille law. The centipoise arose as a convenient submultiple because water conveniently sits near 1 cP, making comparisons intuitive.
Law and Notable Facts
The centipoise is a CGS-derived unit and is not part of the SI, which prefers the pascal-second (Pa·s) or millipascal-second (mPa·s). Because exactly, conversion between the everyday industrial unit and the SI unit requires no arithmetic beyond a change of name — a coincidence that has helped the centipoise survive.
Real-World Examples and Conversions
Water at 20 °C is about 1.002 cP. Whole milk is roughly 3 cP, olive oil around 60–80 cP, and honey near 2,000–10,000 cP. SAE 30 motor oil at 20 °C is on the order of 200 cP. To convert, .
Frequently Asked Questions
How many centipoises are in one lbf·s/ft²?
One pound-force-second per square foot equals about 47,880.26 centipoise.
What factor converts lbf·s/ft² to centipoises?
Multiply the lbf·s/ft² value by 47,880.26.
Why is the imperial unit so much larger than a centipoise?
Because lbf·s/ft² is built from pound-force, foot, and second, it represents a very viscous reference; most everyday fluids are only a few cP.
What is 0.01 lbf·s/ft² in centipoises?
0.01 lbf·s/ft² equals about 478.8 cP (0.01 × 47,880.26).
How does this compare with pascal-seconds?
Since 1 lbf·s/ft² is about 47.88 Pa·s and 1 Pa·s is 1000 cP, the two routes agree at roughly 47,880 cP.
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Complete pound-force-seconds per square foot conversion table
| Unit | Result |
|---|---|
| pascal-seconds (Pa-s) | 47.88026 Pa-s |
| millipascal-seconds (mPa-s) | 47880.26 mPa-s |
| poises (P) | 478.8026 P |
| centipoises (cP) | 47880.26 cP |
| pounds per foot-second (lb/(ft-s)) | 32.17405 lb/(ft-s) |