🔧 Torque Conversion Calculator
Convert between Newton metres, foot-pounds, inch-pounds, kgf·m, kN·m, dyne·cm and 15+ units — with torque definition, power-torque-speed relation, clamping force, preload & bolt stress formulas rendered in MathJax
🔄 Torque Unit Converter
🔩 All Units at Once
📖 How to Use This Torque Conversion Calculator
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1Filter by Unit Category (Optional)
Click SI/Metric (N·m, kN·m, kgf·m, kgf·cm, N·cm), Imperial/US (lb·ft, lb·in, oz·ft, oz·in), or CGS (dyn·cm) to narrow the unit dropdowns. "All Units" shows all 17 units together.
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2Enter Your Torque Value
Type the value into "Enter Value." Any numeric input is accepted — from micronewton metres (µN·m) for electronic components to kilonewton metres (kN·m) for bridge engineering. Scientific notation auto-applies for extreme values.
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3Select From and To Units
Choose source in "From Unit" and target in "To Unit." The result and exact conversion factor appear instantly in the green result box.
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4Use Quick-Convert Buttons
Click N·m→ft·lb, ft·lb→N·m, N·m→in·lb, in·lb→N·m, kN·m→ft·lb, N·m→kgf·m, or kgf·cm→N·m for the most common torque conversions. Both dropdowns set automatically.
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5View All Units & Copy
"All Units at Once" shows your torque in every supported unit simultaneously. Click "📋 Copy Result" to copy the primary conversion to clipboard for technical documents, workshop manuals, or engineering reports.
📐 Torque Unit Conversion Factors Reference
| From | To | Multiply By | Math Expression |
|---|---|---|---|
| 1 N·m | lb·ft | 0.737562 | \( 1\,\text{N·m} = 0.737562\,\text{lb·ft} \) |
| 1 lb·ft | N·m | 1.355818 | \( 1\,\text{lb·ft} = 1.355818\,\text{N·m} \) |
| 1 N·m | lb·in | 8.850745 | \( 1\,\text{N·m} = 8.850745\,\text{lb·in} \) |
| 1 lb·in | N·m | 0.112985 | \( 1\,\text{lb·in} = 0.112985\,\text{N·m} \) |
| 1 lb·ft | lb·in | 12 | \( 1\,\text{lb·ft} = 12\,\text{lb·in} \) |
| 1 kgf·m | N·m | 9.80665 | \( 1\,\text{kgf·m} = g_n \times 1\,\text{m} = 9.80665\,\text{N·m} \) |
| 1 kgf·cm | N·m | 0.0980665 | \( 1\,\text{kgf·cm} = 0.0980665\,\text{N·m} \) |
| 1 kN·m | N·m | 1,000 | \( 1\,\text{kN·m} = 10^3\,\text{N·m} \) |
| 1 N·cm | N·m | 0.01 | \( 1\,\text{N·cm} = 10^{-2}\,\text{N·m} \) |
| 1 dyn·cm | N·m | 1×10⁻⁷ | \( 1\,\text{dyn·cm} = 10^{-7}\,\text{N·m} \) |
🔧 Understanding Torque — A Complete Engineering Guide
Torque is the rotational equivalent of force — the tendency of a force to cause or change the rotation of an object around an axis. While force pushes or pulls an object in a linear direction, torque twists or rotates. Every time you open a jar lid, tighten a bolt with a wrench, turn a steering wheel, or start a motor, torque is the physical quantity doing the mechanical work.
Understanding torque — and accurately converting between its many measurement units — is indispensable in virtually every branch of mechanical engineering, structural engineering, automotive design, aerospace, robotics, and precision manufacturing. A motor specification in a Japanese service manual uses Newton metres (N·m); an American workshop manual specifies the same bolt in foot-pounds (ft·lb); a RC servo datasheets quotes kilogram-centimetres (kgf·cm). Converting accurately between these is not optional — it directly determines whether a fastener holds or fails, whether a motor is correctly specified, and whether a structure is safely loaded.
⚖️ The Newton Metre — SI Standard for Torque
The newton metre (N·m) is the SI derived unit of torque. It equals the torque produced by a force of one newton applied perpendicularly at a distance of one metre from the pivot point. The newton metre is also the SI unit of energy (the joule, J), and while 1 N·m = 1 J mathematically, torque and energy are physically distinct quantities — torque involves a rotational axis, while energy is a scalar. Context always disambiguates: torque is expressed as N·m, energy as J.
The practical range of torque spans an extraordinary scale: from a few µN·m (micronewton metres) for MEMS gyroscopes and precision watch mechanisms, through tens of N·m for automotive fasteners, hundreds of N·m for car engines, thousands of N·m for heavy diesel trucks and electric motors, to millions of N·m for ship propellers and wind turbines.
\( 1\,\text{N·m} = 0.737562\,\text{ft·lb} = 8.850745\,\text{in·lb} = 0.101972\,\text{kgf·m} \)
\( 1\,\text{kN·m} = 1{,}000\,\text{N·m} = 737.562\,\text{ft·lb} \)
\( 1\,\text{kgf·m} = g_n \times 1\,\text{m} = 9.80665\,\text{N·m} \approx 7.233\,\text{ft·lb} \)
\( 1\,\text{kgf·cm} = 0.0980665\,\text{N·m} = 0.8679\,\text{in·lb} \)
🔩 N·m to ft·lb — The Most Common Torque Conversion
The foot-pound (ft·lb or lb·ft) is the imperial unit of torque dominant in US and UK automotive workshops, aviation maintenance (FAA-approved procedures), and American civil engineering. One foot-pound is the torque produced by a one-pound force applied perpendicularly at a distance of one foot from the pivot. Because the international yard and pound were fixed in 1959, the conversion between N·m and ft·lb is exact:
\( 1\,\text{ft} = 0.3048\,\text{m} \quad \text{(exact, 1959 agreement)} \)
\( 1\,\text{lbf} = 0.45359237\,\text{kg} \times 9.80665\,\text{m/s}^2 = 4.448222\,\text{N} \quad \text{(exact)} \)
\( 1\,\text{ft·lb} = 0.3048\,\text{m} \times 4.448222\,\text{N} = 1.355818\,\text{N·m} \quad \text{(exact)} \)
\( 1\,\text{N·m} = \frac{1}{1.355818} = 0.737562\,\text{ft·lb} \)
Problem: A European car manufacturer specifies the wheel lug nut torque as 120 N·m. A US workshop technician needs this in ft·lb to set their torque wrench.
\[ 120\,\text{N·m} \times 0.737562 = \mathbf{88.5\,\text{ft·lb}} \]
Reverse check: \( 88.5\,\text{ft·lb} \times 1.355818 = 120.0\,\text{N·m} \) ✓
Answer: Set the torque wrench to 88.5 ft·lb. Under-torquing risks the wheel loosening at speed; over-torquing risks stud fracture or warping the brake rotor disc. Neither outcome is acceptable — precise conversion is a safety-critical calculation.
🪛 N·m to in·lb — Precision Fastener Engineering
The inch-pound (lb·in or in·lb) is the small-scale imperial torque unit, used where foot-pounds would produce values too small to measure accurately with a standard workshop wrench. Typical applications include: cylinder head valve cover bolts, motorcycle engine side covers, bicycle stem bolts, electronics enclosure fasteners, medical device assemblies, and aerospace avionics racks.
The relationship between inch-pounds and foot-pounds is exact and geometrically obvious — there are exactly 12 inches in one foot, so:
\( 1\,\text{ft·lb} = 12\,\text{in·lb} \quad \text{(exact — 1 foot = 12 inches)} \)
\( 1\,\text{in·lb} = \frac{1}{12}\,\text{ft·lb} = 0.0833\overline{3}\,\text{ft·lb} \)
\( 1\,\text{N·m} = 8.850745\,\text{in·lb} \qquad 1\,\text{in·lb} = 0.112985\,\text{N·m} \)
\( \tau\,[\text{in·lb}] = \tau\,[\text{N·m}] \times 8.850745 \qquad \tau\,[\text{N·m}] = \tau\,[\text{in·lb}] \times 0.112985 \)
Problem: A Yamaha workshop manual specifies valve cover bolts at 10 N·m. Convert to in·lb and ft·lb.
N·m → in·lb: \( 10 \times 8.850745 = \mathbf{88.5\,\text{in·lb}} \)
N·m → ft·lb: \( 10 \times 0.737562 = \mathbf{7.38\,\text{ft·lb}} \)
Insight: At 7.38 ft·lb, most workshop torque wrenches struggle with fine resolution. But an in·lb torque wrench calibrated to 88.5 in·lb gives accurate, repeatable results. This is exactly why in·lb torque specifications exist for small fasteners — optimal measurement range for the tool.
⚡ Torque, Power & RPM — The Fundamental Relationship
Torque and power are fundamentally related through rotational speed. An engine that produces high torque at low RPM is described as having "good low-end pull" — ideal for trucks, tractors, and electric vehicles. An engine with high power achieved through high RPM is described as "revvy" — characteristic of naturally-aspirated sports car engines. This relationship is the reason electric vehicles feel so instant: they deliver maximum torque from 0 RPM.
Problem: An engine specification sheet states: 380 N·m peak torque at 3,000 RPM. Calculate power in kW and horsepower.
\[ P = \frac{2\pi \times 3{,}000 \times 380}{60} = \frac{6.2832 \times 3{,}000 \times 380}{60} = \frac{7{,}162{,}832}{60} = 119{,}381\,\text{W} \approx \mathbf{119.4\,\text{kW}} \]
In horsepower: \( 119{,}381 \div 745.7 = \mathbf{160.1\,\text{hp}} \)
Cross-check in US customary: \( \frac{380\,\text{N·m} \times 0.737562\,[\text{to ft·lb}] \times 3{,}000}{5{,}252} = \frac{280.3 \times 3{,}000}{5{,}252} = \mathbf{160.1\,\text{hp}} \) ✓
🔩 Bolt Preload & Clamping Force — Why Torque Specs Matter
When you tighten a bolt to a specific torque, the goal is not torque itself — it is the clamping force (preload) that torque creates by stretching the bolt. The torque specification in a service manual is an indirect way to specify the desired bolt elongation and the clamping force it generates. Understanding this distinction explains why torque specifications are so critical: they are ultimately a proxy for a structural force.
\( T = K \cdot d \cdot F \qquad \text{(Torque–Preload equation)} \)
\( F = \frac{T}{K \cdot d} \qquad \text{(solving for clamping force)} \)
\( \sigma = \frac{F}{A_s} \qquad \text{(bolt stress from preload)} \)
\( \delta = \frac{F \cdot L}{E \cdot A} \qquad \text{(bolt elongation / stretch)} \)
Problem: An M12 × 1.75 steel bolt is torqued to 80 N·m on a dry thread. What clamping force is generated? (K = 0.20 for dry, d = 0.012 m)
\[ F = \frac{T}{K \cdot d} = \frac{80}{0.20 \times 0.012} = \frac{80}{0.0024} = \mathbf{33{,}333\,\text{N}} = \mathbf{33.3\,\text{kN}} \]
With engine oil lubrication (K = 0.14): \( F = 80 / (0.14 \times 0.012) = 47{,}619\,\text{N} = 47.6\,\text{kN} \)
Critical finding: Lubricating the thread increases clamping force by 43% for identical torque! This is why workshop manuals always specify "dry torque" or "lubricated torque" — they are different specifications, not interchangeable. Using the dry torque spec on lubricated threads risks bolt fracture.
🤖 kgf·cm — Servo Motors, Robotics & Micro-Engineering
The kilogram-force centimetre (kgf·cm) is the standard torque unit in the RC hobby, robotics, and consumer servo motor industries worldwide. It represents the torque produced by a one-kilogram force acting perpendicularly at a radius of one centimetre. Despite not being an SI unit, it is universally used in servo datasheets because it maps intuitively to the physical test used to rate servos: attach a lever arm and measure how many grams (or kilograms) it can hold at a given radius.
\( 1\,\text{kgf·cm} = 1\,\text{kg} \times 9.80665\,\text{m/s}^2 \times 0.01\,\text{m} = 0.0980665\,\text{N·m} \)
\( 1\,\text{N·m} = \frac{1}{0.0980665} = 10.1972\,\text{kgf·cm} \)
\( \tau\,[\text{kgf·cm}] = \tau\,[\text{N·m}] \times 10.1972 \)
\( \tau\,[\text{N·m}] = \tau\,[\text{kgf·cm}] \times 0.0980665 \)
🌍 Real-World Torque Reference Table
| Application | Typical Torque (N·m) | In ft·lb | In in·lb |
|---|---|---|---|
| ⌚ Luxury watch screw | 0.001–0.010 | 0.00074–0.0074 | 0.009–0.088 |
| 🤖 RC micro servo (5 kgf·cm) | 0.49 | 0.36 | 4.3 |
| 💻 Laptop hinge bolt | 0.5–1.5 | 0.37–1.11 | 4.4–13.3 |
| 🔩 Bicycle stem bolt | 5–8 | 3.7–5.9 | 44–71 |
| 🏍️ Motorcycle valve cover | 8–12 | 5.9–8.9 | 71–106 |
| 🚗 Spark plug (automotive) | 20–30 | 14.8–22.1 | 177–265 |
| 🔧 Wheel lug nut (passenger car) | 80–140 | 59–103 | 708–1,239 |
| 🚗 Economy car engine (peak) | 150–220 | 111–162 | 1,327–1,947 |
| 🏎️ Performance car engine (peak) | 400–700 | 295–516 | 3,540–6,195 |
| ⚡ Tesla Model S Plaid (motor) | ~1,840 | ~1,357 | ~16,283 |
| 🚚 Heavy diesel truck (peak) | 1,000–3,000 | 738–2,213 | 8,851–26,552 |
| 🚢 Large ship propeller shaft | 50,000–500,000 | 36,878–368,781 | — |
📦 Torque Unit System Guide
Newton Metre (N·m)
SI unit. 1 N·m = 1 J = force of 1 N at 1 m radius. Global engineering standard. All service manuals outside North America use N·m exclusively. Never confuse with joules (same dimensions, different physical context).
Foot-Pound (ft·lb)
US/UK imperial unit. 1 ft·lb = 1.355818 N·m. SAE standard for all US automotive, aviation (FAA AC 43.13), and US military specifications. Note: "ft-lb" and "lb-ft" both appear in practice, always meaning the same unit.
Inch-Pound (in·lb)
Small-scale imperial unit. 1 in·lb = 1/12 ft·lb = 0.112985 N·m. Used for small fasteners: electronics, avionics, medical devices, bicycle components. 1 N·m = 8.85 in·lb — quick rule: ×9 for rough N·m→in·lb.
kgf·cm (Servo/Robotics)
Non-SI gravitational unit. 1 kgf·cm = 0.0980665 N·m. Universal in RC servos, stepper motors, hobby robotics. "10 kg·cm servo" = 0.981 N·m. Convert to N·m: multiply kgf·cm × 0.0981.