Pounds-force to Tons-force (long) (lbf to tonf (UK))

1 pound-force equals 0.0004464285714 tons-force (long) (rounded).

How to convert pounds-force to tons-force (long)

To convert pounds-force to tons-force (long), multiply the number of pounds-force by 0.0004464285714. The factor is rounded to 10 significant digits. To go the other way, multiply tons-force (long) by 2,240.

tons-force (long) = pounds-force × 0.0004464285714

Example: 10 pounds-force = 0.004464285714 tons-force (long).

About these units

Pound-force (lbf)

US & ImperialCurrent unit

Exactly 4.4482216152605 newtons: the weight of a one-pound mass under standard gravity. The US unit of force.

People have used the pound-force since the eighteenth century for low-precision work, long before anyone needed to define it carefully. A pound of material on Earth's surface pulls with about a pound of force, which made it convenient to treat the two as one. The twentieth century demanded a precise definition: one pound-force is the avoirdupois pound, exactly 0.45359237 kg, multiplied by standard gravity of 9.80665 meters per second squared, which comes to about 4.448 newtons.

Because the unit is not simply mass times acceleration in its own system, formulas in English engineering units need a conversion constant of about 32.174 pound-feet per pound-force second squared. A slug, 32.174049 pounds of mass, is what one pound-force accelerates at one foot per second squared. In the US, jet and rocket thrust is often given as pounds of thrust: each Space Shuttle solid rocket booster produced 3,300,000 pounds-force. Earth's gravity varies by up to about half a percent between equator and pole, which low-precision work can ignore.

1 pound-force = 4.448221615 newtons (approximately).

Sources: Wikipedia: Pound (force); NIST Guide to the SI, Appendix B.8: conversion factors

Ton-force (long) (tonf (UK))

Imperial (British)Traditional unit (still used in some regions)

2,240 pounds-force (9.964 kN), the weight of a long ton.

Weighing a British long ton of mass under standard gravity gives this unit: 2,240 pounds-force, or about 9.964 kN (the more exact figure is 9.96401641818352 kN). It belongs to the imperial family and, per Wikipedia, equals roughly 1,016.05 kilograms-force, which makes it a heavy unit suited to large structures, ships and machinery described in British units.

Confusion with its neighbours is the main hazard. The short ton-force of 2,000 lbf, common in the United States, is about 8.896 kN, so one long ton-force equals 1.12 of them. The metric tonne-force, 1,000 kgf, is 9.80665 kN, a little smaller, since the long ton-force is about 1.016 of it. NIST lists only the 2,000 lbf version, a hint of how rarely the long form is now met.

1 ton-force (long) = 9,964.016418 newtons (approximately).

Sources: Wikipedia: Ton-force; Wikipedia: Pound (force); NIST SP 811, Appendix B.8

Related conversions

See all force units.