Torque Converter

A torque converter translates any moment value between five common engineering units: newton-metres (N·m), pound-force feet (lbf·ft), pound-force inches (lbf·in), kilogram-force metres (kgf·m), and ounce-force inches (ozf·in). Edit any one of the five fields and the other four update in real time through a single N·m pivot, so you never have to do the arithmetic by hand. Mechanics use it to confirm wheel torque specs, bicycle assemblers use it to dial in carbon-component clamp loads, aerospace technicians use it to verify fastener ratings, electronics technicians use it to tighten small screws without stripping them, and engineers use it to read datasheets printed in unfamiliar units. Because torque has the same dimensional form as energy (both reduce to N·m in SI), it is one of the most-misread quantities in shop-floor work, the converter exists specifically to remove that ambiguity.

How to Use the Torque Converter

1. Type a number into any one of the five fields, Newton-metres, kilogram-force metres, pound-force feet, pound-force inches, or ounce-force inches.
2. The other four fields update instantly, all pivoted through the same underlying N·m value, so you cannot get inconsistent answers across fields.
3. Read the equivalent value in the unit your wrench, datasheet or service manual calls for. Most North American automotive tools use lbf·ft, most European and Asian tools use N·m, and most torque-watch and micrometer-clamp displays use either N·m or lbf·in depending on size.
4. Use the Copy button under any field to grab the precise converted value (to the converter's full internal precision) for pasting into a work order or spreadsheet.
5. To reset, clear the field you are typing in, the others will fall back to the seed value, or type a fresh value into any one of them to redefine the moment.
6. For directional work (clockwise vs counter-clockle torque, breakaway vs snug), use the converted value as the target setting on your torque wrench; the converter only handles magnitude, not direction.

The Formulas: Conversion via the N·m Pivot

Every conversion in this tool passes through the SI unit, the newton-metre. Once a value is expressed in N·m, dividing by any unit's exact factor yields the equivalent in that unit. The conversion factors below are exact (or exact to the displayed digits) under NIST SP 811 and the BIPM SI Brochure, 9th edition, and they match the round-numbered equivalents published in ISO 80000-4 and SAE J1701.

Defined conversion factors (each is exact, or exact to the digits shown):

• 1 lbf·ft = 1.3558179483314004 N·m
• 1 lbf·in = 0.1129848290276167 N·m
• 1 kgf·m = 9.80665 N·m
• 1 ozf·in = 0.00706155183333 N·m
• 1 N·m = 1 N·m (the SI base)

Direction A, Convert into N·m: multiply the source value by its factor above. For example, 75 lbf·ft × 1.3558179483314004 = 101.686 N·m.

Direction B, Convert out of N·m: divide the N·m value by the factor of the target unit. For example, 101.686 N·m ÷ 1.3558179483314004 = 75 lbf·ft. Equivalently, multiply by the reciprocal: 101.686 × (1 / 1.3558179483314004) = 75 lbf·ft.

Why a pivot at N·m and not, say, lbf·ft? The BIPM SI Brochure (9th ed.) defines the newton-metre as the coherent SI unit of torque, so every conversion factors out cleanly. Going through any other unit would force an extra multiplication and a small rounding loss per step. The pivot also lets one definition feed every pair: N·m ↔ kgf·m, N·m ↔ lbf·ft, N·m ↔ lbf·in, N·m ↔ ozf·in are all single-factor converts.

Sub-relationship between the inch-pound and foot-pound: because one foot is exactly twelve inches, 1 lbf·ft = 12 lbf·in exactly. This identity is independent of the SI factors above and is a useful sanity check: if a value in lbf·in reads twelve times the value in lbf·ft, the input is consistent. Drop the identity and you lose an entire class of off-by-twelve errors.

Why each factor is what it is. The lbf·ft factor follows from the definition of the pound-force (4.4482216152605 N exactly) multiplied by 0.3048 m/ft exactly, giving 1.3558179483314004 N·m. The lbf·in factor is that value divided by 12. The kgf·m factor is the BIPM standard value of the kilogram-force (9.80665 N exactly) multiplied by one metre. The ozf·in factor is the lbf·in value divided by 16, because one pound is sixteen ounces.

Worked Examples

The four examples below cover the most common shop-floor conversions. Each one shows the multiplication step explicitly so you can reproduce the answer with a pocket calculator.

Example 1, A 100 N·m torque expressed in pound-force feet.

A European service manual specifies 100 N·m for an engine mounting bolt. The technician's click-type wrench is calibrated in lbf·ft.

100 N·m ÷ 1.3558179483314004 = 73.7562 lbf·ft

So 100 N·m ≈ 73.76 lbf·ft. Round to one decimal place (73.8) for everyday wrench work; keep all four decimals when logging the value to a maintenance record.

Example 2, A 50 lbf·ft specification converted to newton-metres.

A US-market shop manual lists a wheel-bearing retainer torque of 50 lbf·ft. The metric equivalent is needed because the shop's digital torque-angle gauge reads N·m.

50 lbf·ft × 1.3558179483314004 = 67.7909 N·m

Rounded, 50 lbf·ft ≈ 67.8 N·m. The gauge should be set to 67.8 N·m; rounding to 68 N·m introduces roughly a 0.3% error, well inside the typical ±2% wrench tolerance.

Example 3, A 1 kgf·m tool setting in both N·m and lbf·ft.

An older Japanese bicycle torque wrench is marked in kgf·m, a unit that is no longer preferred but is still common on legacy tools. The required clamp load is 1 kgf·m.

In newton-metres: 1 kgf·m × 9.80665 = 9.80665 N·m (exact, because the kgf is defined as exactly 9.80665 N).

In pound-force feet: 9.80665 N·m ÷ 1.3558179483314004 = 7.2330 lbf·ft.

A modern carbon-component spec of 5 N·m for a seatpost clamp is well below 1 kgf·m, so on a kgf·m wrench the reading would be roughly 0.51 kgf·m, at the bottom of the scale where these tools are least accurate. Always cross-check with a modern N·m wrench for low-value critical fasteners.

Example 4, A 100 lbf·in precision-driver setting in N·m, plus a 10 N·m small-screw value in ozf·in.

A precision electric screwdriver (for laptops, watches, phones) is rated in lbf·in. The desired clamp is 100 lbf·in.

100 lbf·in × 0.1129848290276167 = 11.2985 N·m.

For an even smaller fastener where the spec is 10 N·m, the same driver reads the inverse: 10 N·m ÷ 0.00706155183333 = 1416.12 ozf·in. That is a useful number for an imperial torque-watch tool, which is sometimes the only instrument available on a small-screw assembly bench.

Where Torque Conversion Shows Up

Automotive lug nuts and head bolts. Wheel removal is the single most-common torque task in the world. A typical passenger-car lug-nut specification falls roughly in the 100 to 140 N·m range, and head bolts on a modern four-cylinder engine commonly land between 60 and 110 N·m depending on bolt size and material. Always use the manufacturer's figure for the specific vehicle and wheel, alloy wheel nuts on aluminium hubs and steel wheel nuts on steel hubs are not the same. Head bolts almost always require a multi-step sequence (torque-to-yield, angle-tightening) that is not captured by a single value.

Bicycle assembly, especially carbon components. A carbon handlebar clamp is typically specified around 5 N·m, a carbon seatpost around 5 N·m, and a carbon stem faceplate around 4 N·m. Steel-component specs run much higher, a bottom bracket is often 40 to 70 N·m, a cassette lockring 40 N·m, and a pedal 35 N·m. Over-torquing carbon is a permanent-damage failure mode (the part cracks), and the carbon-specific specs sit well below the accuracy threshold of cheap beam-type wrenches. A good 1/4-inch click-type wrench with a 5 N·m scale is the standard tool.

Aerospace fasteners. Aircraft primary-structure bolts are tightly specified and audited. Values typically land in the 10 to 200 N·m range depending on bolt diameter and material, but the exact figure depends on the part number, the hole-fit class, and the lubrication state. Conversions between N·m and lbf·in are routine because the global aerospace supply chain mixes metric and imperial documentation. Always use the figure from the maintenance manual for the specific airframe; never generalise.

Electronics and small-screw assembly. Laptops, smartphones, game consoles, and watches use screws on the order of 0.1 to 0.5 N·m, well below the typical 1 N·m threshold of a hardware-store wrench. A 0.5 N·m spec, for example, is 4.43 lbf·in, and a 0.1 N·m spec is 0.886 lbf·in. These values are read off in ozf·in or lbf·in on the small electric and pneumatic drivers used in service centres.

Machining spindles. CNC spindle drawbars, toolholders, and chuck collets have torque specs published by the manufacturer, HSK, CAT, BT, and ER collet toolholders all have specific clamping torques that usually fall in the 30 to 120 N·m range for the nut, with the cutting-tool holding torque being a derived value. Conversion between N·m and lbf·ft is the most common shop-floor conversion in a machine shop.

Common Mistakes

The single most damaging error: confusing lbf·ft with lbf·in. They look almost identical on a printout, and a factor-of-twelve slip will either strip a thread (over-torque by 12×) or under-tighten a safety fastener (under-torque by 12×, leaving it loose). A 50 lbf·ft wheel-nut spec is 600 lbf·in, not 50 lbf·in. The 12× identity (1 lbf·ft = 12 lbf·in, exactly) means the typo is always catastrophic in one direction or the other. Use the converter every time you see both units in the same manual.

Confusing torque with energy. Both have the same SI dimensions (N·m = J), so dimensional analysis cannot distinguish them. Torque is a moment, force applied perpendicular to a lever arm, and is measured in N·m. Energy is work done, force times displacement along the direction of motion, and is measured in joules (also written N·m in SI but never in mixed contexts). A torque of 100 N·m is not 100 J of energy; you cannot convert torque to energy without also specifying the angle of rotation.

Assuming kgf·m equals N·m. A kilogram-force metre is 9.80665 N·m, not 1 N·m. Reading a kgf·m wrench value as if it were N·m under-torques by a factor of almost 10×, for example, 1 kgf·m on the dial is 9.81 N·m of clamp, not 1 N·m. This is a particularly common error with older Japanese tools that still use the legacy kgf·m scale.

Forgetting about friction. The torque you set on a wrench is the clamping torque, which is roughly 80 to 90% absorbed by the thread friction and bolt-head friction in a typical steel-on-steel bolt. The remaining 10 to 20% is the useful preload (clamp force times thread pitch). Lubrication dramatically changes this split, a well-lubricated bolt at the same wrench setting develops substantially more preload, which is why torque specs are lubrication-specific.

Rounding too aggressively too early. A 50 N·m spec rounded to 50 lbf·ft is 7% off (50 N·m ≈ 36.88 lbf·ft). Round only at the end of the calculation, and keep at least three significant digits in the intermediate steps.

Frequently Asked Questions

What is the exact conversion factor between lbf·ft and N·m?

The exact factor is 1 lbf·ft = 1.3558179483314004 N·m. It is exact because both inputs are exact in their respective definitions: 1 lbf = 4.4482216152605 N exactly (NIST SP 811), and 1 ft = 0.3048 m exactly. Multiplying these together gives the factor to sixteen significant digits with no rounding.

How do I convert N·m to lbf·in for a small-screw driver?

Divide the N·m value by 0.1129848290276167. As an example, 5 N·m ÷ 0.1129848290276167 ≈ 44.25 lbf·in. The inverse relationship (1 lbf·in = 0.1129848290276167 N·m) is exact and follows from dividing the lbf·ft factor by 12.

Why do mechanics in different countries use different torque units?

The legacy unit system drove the original choice, pound-force feet and pound-force inches for imperial-system countries, kilogram-force metres for the older metric-system countries (especially Japan and pre-SI Germany), and newton-metres for the modern SI-coherent system. Modern automotive and aerospace manuals are migrating to N·m globally, but legacy tools and older service procedures still use the historical units, which is why a converter that handles all five is useful.

Is torque the same thing as work or energy?

No, although torque and energy both reduce to N·m in SI units, they are different physical quantities. Torque is a moment (force × perpendicular lever arm), measured in N·m. Energy is work (force × displacement along the direction of motion), measured in joules (also dimensionally N·m but conceptually distinct). The dimensional coincidence is a famous source of confusion in introductory physics; it does not mean the quantities can be interchanged.

What torque wrench should I use for bicycle carbon parts?

For carbon handlebar, stem, and seatpost clamps (typically 4 to 6 N·m), a 1/4-inch drive click-type wrench with a scale that resolves 0.1 N·m or finer is the standard recommendation. Beam-type wrenches are usually not accurate enough below about 5 N·m. A pre-set or torque-limiting bit driver (for hex, Torx, or other sockets) is also acceptable. Always use the manufacturer's specified torque value for the specific component, never a generic value.

Why does 1 lbf·ft equal exactly 12 lbf·in?

Because 1 foot is exactly 12 inches. Both units use the same pound-force, so the only difference is the lever arm: 1 lbf·ft = 1 lbf × 1 ft, and 1 lbf·in = 1 lbf × 1 in. Therefore 1 lbf·ft = 1 lbf × 12 in = 12 lbf·in exactly. This identity is independent of the SI factors and holds to arbitrary precision, which makes it a reliable sanity check on every torque calculation that involves both units.

Can I trust a 1/4-inch click wrench at very low torque values (under 1 N·m)?

Most general-purpose 1/4-inch click wrenches are accurate to roughly ±4 to ±6% of the indicated value in the middle of their scale, with degraded accuracy at the very bottom of the scale (below about 10% of full-scale). For under-1 N·m work, especially in electronics and watchmaking, a calibrated torque-limiting bit driver or a digital torque screwdriver is the appropriate tool. The converter will give you the right number; the wrench accuracy is a separate question.

What does "ft-lb" mean, and is it the same as lbf·ft?

Yes, "ft-lb" is an older notation for what is now properly written lbf·ft (pound-force foot). The order of the units matters: torque is force × distance, and the conventional notation puts the force unit first. The two notations refer to the same physical quantity, and the converter accepts both, but in modern usage lbf·ft is preferred because it makes the distinction from lbf·in (which is 1/12 as much) unambiguous.

References

• NIST Special Publication 811, Guide for the Use of the International System of Units (SI). The authoritative US reference for SI usage and unit conversion. The values of the pound-force (4.4482216152605 N) and the foot (0.3048 m) used in the lbf·ft factor are defined here.
• BIPM SI Brochure (9th edition), The International System of Units (SI). Published by the Bureau International des Poids et Mesures, this is the canonical definition of the SI units, including the newton, the metre, and the convention that torque is measured in N·m.
• ISO 80000-4, Quantities and units, Part 4: Mechanics. The international standard for the quantities, symbols, and units of mechanics, including torque (symbol T or M, unit N·m) and the relationships among gravitational, mass, and force units.
• SAE J1701, Torque Ratings, English/Metric Equivalents. The Society of Automotive Engineers standard that tabulates the common engineering conversions between imperial and metric torque units, used widely in the automotive industry for tool and fastener specifications.