Torque Converter
By KAMP Inc. / UnitOwl · Last reviewed:
Torque is the rotational equivalent of force — it describes how effectively a force causes an object to rotate around an axis. From tightening a lug nut to measuring engine output, torque is central to automotive engineering, manufacturing, and everyday fastener work. The two dominant units — pound-feet (lb·ft) in the US and Newton-meters (N·m) everywhere else — reflect the broader metric vs. imperial divide, and mixing them up can mean under-torqued bolts or stripped threads.
Popular Torque Conversions
Newton-Meters vs. Pound-Feet: The Global Divide
The Newton-meter (N·m) is the SI unit of torque: the torque produced by a force of one newton acting at a perpendicular distance of one meter from the pivot. It is used universally in engineering, science, and virtually all countries outside the United States. The pound-foot (lb·ft, sometimes written ft·lb) is the US customary unit: the torque of one pound-force acting at one foot from the pivot. One lb·ft equals approximately 1.356 N·m. Do not confuse pound-feet (torque) with foot-pounds (energy) — they are dimensionally identical but conceptually different. Automotive specs in the US use lb·ft; the same engine's specs in Europe appear in N·m. A 300 lb·ft gasoline engine produces about 407 N·m.
| Unit | Equivalent |
|---|---|
| 1 N·m | 0.7376 lb·ft |
| 1 lb·ft | 1.3558 N·m |
| 1 kgf·m | 9.8066 N·m |
| 1 oz·in | 0.00706 N·m |
| 100 N·m | 73.76 lb·ft |
| 300 lb·ft | 406.7 N·m |
Engine Torque and Automotive Applications
Engine torque is arguably the most common real-world torque value consumers encounter. It measures the rotational force an engine produces at the crankshaft and determines how quickly a vehicle accelerates from low speeds. A typical economy car produces 120–180 N·m (90–130 lb·ft); a performance SUV might produce 400–600 N·m (295–442 lb·ft); heavy-duty diesel trucks can exceed 2,700 N·m (2,000 lb·ft). Torque peaks at a specific RPM range — diesel engines tend to peak at lower RPM (1,500–2,500) while gasoline engines peak higher (3,000–5,000 RPM). For drivers, torque translates to pulling power: towing capacity and off-the-line acceleration are torque-limited, not horsepower-limited.
Fastener Torque: Getting It Right
For anyone wrenching on vehicles, machinery, or bicycles, torque specs matter. Overtightening a bolt can strip threads, crack components, or cause fastener fatigue failure. Under-tightening a critical fastener — a wheel lug nut, for instance — can cause catastrophic loosening at speed. Torque wrenches are rated in lb·ft, lb·in (inch-pounds), or N·m. For delicate work like bicycle components or electronics, inch-pounds and centi-Newton-meters are more practical: 1 lb·in = 0.113 N·m. Cylinder head bolts on a typical car engine require 80–100 lb·ft (108–136 N·m); wheel lug nuts typically require 80–120 lb·ft (108–163 N·m). Always use the torque spec in the service manual — guessing can cause expensive damage.
Sources & References
- NIST — Units and Conversion Factors — Official unit conversion factors from the National Institute of Standards and Technology.
- BIPM — The International System of Units (SI) — International SI unit definitions from the International Bureau of Weights and Measures.