About

Torque specifications in mechanical engineering often vary based on the origin of the machinery. European and Japanese legacy manuals frequently use Kilogram-force meters (kgf·m), while modern ISO standards and academic physics rely on Newton-meters (N·m). This discrepancy can lead to critical over-tightening or under-tightening of bolts if not converted accurately.

This tool utilizes the standard acceleration of gravity defined by ISO 80000-3. Unlike approximate mental math which assumes a multiplier of 10, this calculator applies the precise constant g ≈ 9.80665 m/s². This precision is non-negotiable for engine rebuilding, hydraulic system calibration, and structural engineering tasks where safety factors are tight.

Formulas

The conversion relies on the definition of force where 1 kgf is the force exerted by one kilogram of mass in standard gravity.

1 kgf·m = 1 kg × g × 1 m

Standard: g ≈ 9.80665 m/s²

Therefore: T_Nm = T_kgf·m × 9.80665

Reference Data

kgf·m	Precision N·m (g=9.80665)	Rough N·m (g=10)	Application Context
1	9.81	10	Bicycle components
5	49.03	50	Spark plugs
10	98.07	100	Car lug nuts (small)
12	117.68	120	Standard lug nuts
25	245.17	250	Axle nuts
50	490.33	500	Heavy truck lugs
100	980.67	1000	Industrial machinery

Frequently Asked Questions

This value was adopted by the 3rd CGPM in 1901 as the standard acceleration due to gravity on Earth. While gravity varies slightly by latitude and altitude, 9.80665 is the universal constant for defining the kilogram-force unit.

For non-critical applications (like assembling simple furniture), rounding to 10 is often acceptable (2% error). However, for engine head bolts or suspension components, a 2% variance combined with tool tolerance can lead to failure. Always use the precise value.

No. The conversion is between units of torque (Force × Distance). The physical length of the tool is irrelevant to the unit conversion itself, though it affects how much force you personally apply.

kg·m implies Moment of Inertia (mass × distance squared) or unscientific shorthand. kgf·m explicitly refers to Kilogram-Force meters (force × distance), which is a unit of torque. In casual shop talk, "kilos" usually means kgf·m.