Torque from one pound-force at one foot.
Pound-feet to Femtonewton meters Converter — lb ft to fN m
Convert Pound-foot (lb ft) to Femtonewton meter (fN m) using the exact conversion factor (1 pound-foot = 1.355818e+15 femtonewton meter). See the formula, worked examples, conversion table, history, and common uses.
Pound-feet to Femtonewton meters converter
Converter
Engineering Converter
Convert common stress, force, torque, power, and energy units used in engineering.
Context values
Some unit families need one extra value for a physically accurate result.
Femtonewton meter is 1e-15 newton meter units.
Result = input x 1.355817948 / 1e-15.
Torque units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Pound-feet to Femtonewton meters
Pound-foot and Femtonewton meter both measure a quantity used in structural or mechanical engineering — commonly stress, pressure, force, torque, power, or energy — where converting between the unit conventions used in different regions, industries, or equipment specifications is a routine part of design work. Pound-foot is most often used for us torque wrench specifications (bolt tightening).
Formula
femtonewton meters = pound-feet × 1.355818e+15
This factor comes from each unit's defined relationship to the category's base unit: 1 pound-foot equals 1.35581794833 base units, and 1 femtonewton meter equals 1e-15 base units, so dividing one by the other gives the direct pound-foot-to-femtonewton meter factor of 1.355818e+15.
Simple example
1 lb ft × 1.355818e+15 = 1.355818e+15 fN m
1 pound-foot = 1.355818e+15 femtonewton meters.
Real-world example
100 lb ft × 1.355818e+15 = 1.355818e+17 fN m
100 pound-feet = 1.355818e+17 femtonewton meters.
Conversion table
| Pound-foot (lb ft) | Femtonewton meter (fN m) |
|---|---|
| 1 lb ft | 1.355818e+15 fN m |
| 10 lb ft | 1.355818e+16 fN m |
| 50 lb ft | 6.77909e+16 fN m |
| 100 lb ft | 1.355818e+17 fN m |
| 500 lb ft | 6.77909e+17 fN m |
| 1,000 lb ft | 1.355818e+18 fN m |
Reverse conversion: Femtonewton meter to Pound-foot
1.355818e+15 fN m × 7.375621e-16 = 1.000000038 lb ft
1.355818e+15 femtonewton meters = 1.000000038 pound-feet.
pound-feet = femtonewton meters × 7.375621e-16
For a page dedicated to this direction, see Femtonewton meter to Pound-foot.
Understanding the Pound-foot
Pound-foot (lb ft) measures torque. A pound-foot is the torque from one pound-force applied at one foot of leverage: exactly 1.3558179483314004 newton-meters. It is classified as a US/imperial customary unit.
Where it's used: United States (automotive and mechanical torque specifications)
Pound-foot vs. foot-pound. Pound-foot (torque) and foot-pound (energy/work) use the same two units but measure physically different quantities; US convention typically orders them differently to help distinguish which is meant, though usage isn't always consistent.
Uses of the Pound-foot today
- US torque wrench specifications (bolt tightening)
- US automotive engine torque specifications
- US mechanical and construction trades
History of the Pound-foot
The pound-foot follows from pound-force and the foot, both standardized through English and later international agreements, remaining the standard US automotive and mechanical torque unit even as most other measurements shifted toward metric in engineering contexts.
Historical origin. Pound-foot was not the invention of a single named person; it developed through the process described above.
Understanding the Femtonewton meter (fN m)
Femtonewton meter is 1e-15 newton meter units.
Pound-foot — sources
- NIST Special Publication 811 — Documents the pound-foot's exact newton-meter equivalence.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many femtonewton meters are in 1 pound-foot?
1 pound-foot equals 1.355818e+15 femtonewton meters, using the exact defined conversion factor rather than an estimate.
How do I convert pound-foot to femtonewton meter?
Multiply the pound-foot value by 1.355818e+15. The converter above does this instantly to whatever precision you set.
How do I convert femtonewton meter back to pound-foot?
Use the reverse factor: 1 femtonewton meter equals 7.375621e-16 pound-feet. You can also use the swap control in the converter above to flip the direction instantly.
What is a pound-foot?
Pound-foot (lb ft) measures torque. A pound-foot is the torque from one pound-force applied at one foot of leverage: exactly 1.3558179483314004 newton-meters. It is classified as a US/imperial customary unit.
What is a femtonewton meter?
Femtonewton meter (fN m) is a unit of engineering.
Is the pound-foot to femtonewton meter conversion exact?
Yes. A pound-foot is the torque from one pound-force applied at one foot of leverage: exactly 1.3558179483314004 newton-meters. That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
What is the difference between pound-foot vs. foot-pound?
Pound-foot (torque) and foot-pound (energy/work) use the same two units but measure physically different quantities; US convention typically orders them differently to help distinguish which is meant, though usage isn't always consistent.
Where is the pound-foot still used today?
United States (automotive and mechanical torque specifications)