Engineering Units and Conversions

Conversion factors for force, moment, pressure, stress, length, mass, density, acceleration, temperature, energy, power and frequency.

Article 11.01Units & Conversions4 min read

unitsconversionSIimperialforcepressurestresslengthmasstemperature

Force

From	To	Multiply by
N	kN	0.001
N	lbf	0.22481
lbf	N	4.4482
kN	kip	0.22481
kip	kN	4.4482
kgf	N	9.8067

Moment / Torque

From	To	Multiply by
N·m	N·mm	1000
N·m	lbf·ft	0.73756
lbf·ft	N·m	1.3558
N·mm	lbf·in	8.8507
lbf·in	N·mm	112.98
kN·m	kip·ft	0.73756

Stress and Pressure

From	To	Multiply by
Pa	MPa	1 × 10⁻⁶
MPa	Pa	1 × 10⁶
MPa	psi	145.038
psi	MPa	0.006895
ksi	MPa	6.895
MPa	ksi	0.145038
Pa	bar	1 × 10⁻⁵
bar	Pa	1 × 10⁵
MPa	bar	10
N/mm²	MPa	1 (exact)

Length and Area

From	To	Multiply by
mm	m	0.001
mm	in	0.039370
in	mm	25.4 (exact)
m	ft	3.2808
ft	m	0.3048 (exact)
mm²	in²	0.001550
in²	mm²	645.16
mm⁴	in⁴	2.4025 × 10⁻⁶
in⁴	mm⁴	416231

Mass and Density

From	To	Multiply by
kg	lb	2.2046
lb	kg	0.45359
g/cm³	kg/m³	1000
kg/m³	g/cm³	0.001
g/cm³	lb/in³	0.036127
lb/in³	g/cm³	27.680
kg/m³	lb/ft³	0.062428

Acceleration and Energy

From	To	Multiply by
g (standard)	m/s²	9.80665
m/s²	g	0.10197
J	N·m	1 (exact)
J	ft·lbf	0.73756
ft·lbf	J	1.3558
kJ	Btu	0.94782
W	J/s	1 (exact)
kW	hp	1.3410
hp	kW	0.74570

Temperature

T(K)   =  T(°C) + 273.15
T(°F)  =  (9/5) · T(°C) + 32
T(°C)  =  (5/9) · (T(°F) − 32)

Temperature differences:
ΔT(K)  =  ΔT(°C)   (identical increments)
ΔT(K)  =  (5/9) · ΔT(°F)
ΔT(°F) =  (9/5) · ΔT(K)

Notes

SI is the primary system throughout this Reference Library
1 N/mm² = 1 MPa exactly
Standard gravity g₀ = 9.80665 m/s² (defined, not measured)
Do not confuse mass (kg) with force (N) — weight is a force: W = m · g

Related Knowledge

See Engineering Constants for SI prefixes and fundamental constants.

Engineering Constants