For the Oil&Gas community, this app is a really useful tool that lets you convert from various units into others which are commonly used on the oilfield.
Length(m,cm,mm,ft,in,1/32in)
Area(m2,ft2,yd2,in2,acre)
Volume(m3,cm3,in3,ft3,liter(l),barrel(bbl),US gal,UK gal)
Density(kg/m3,g/cm3,kg/l,sg,lbm/ft3,lbm/USgal)
Temperature(Kelvin,Celsius,Fahrenheit,Rankin)
Temperature Gradient (K/m,C/m,F/ft)
Angle(radians,degrees)
Force(N,KN,lbf,dyne)
Power(W,KW,hp)
Fluid / Tripping Velocity(m/s,m/min,m/hr,ft/s,ft/min,ft/hr)
Pump / Flow Rate(USgal/min,m3/sec,m3/min,m3/hr,l/min,ft3/min,ft3/hr,bbl/min)
Pressure(Pa,KPa,MPa,bar,psi,lbf/ft2)
Pressure Gradient(Pa/m,bar/m,psi/ft)
Torque(N.m,KN.m,lbf.ft,lbf.in)
Viscosity(Pa.s,cp,dyne.s/cm2,lbf.s/ft2,lbf.s/in2)
Thermal Conductivity(W/(m.K),W/(cm.C),Btu/(hr.ft.F),Btu/(min.m.F),Btu/(hr.m.F))
Heat Capacity(J/(Kg. K),J/(g. C),KJ/(Kg. K),Btu/(lbm. F))