I've got the typical density of reinforced concrete - 17 to 24kN/m3. But I need it in kg/m3 format. anyone know how to do this?

Density in newtons per meter cubed!?! weird afaik it should be a case of g=9.81ms^-2 and F=M.A so M=F/A (Keep in mind Newtons are the SI unit for force and Kg are the SI unit for mass) 17000/9.81=1732kg/m^3 to 24000/9.81=2446kg/m^3

They are different dimensioned units. One is a mass per cubic metre and one is a force per cubic metre. The most common way of converting a static mass to a force is to multiply it by the acceleration due to earth's gravity. An easy rule of thumb is 10 but more accurately it is 9.81. Cheers, Nigel

1kgf (kilogram of force) = 9.807 Newtons. So to convert kN to kg, divide by 9.807. Strictly speaking, that's only meaningful in standard gravity, but the conversion factor applies universally. ===== EDIT ==== MightyG's done it for you.

Sorry, pedant alert. It can't apply universally because it varies greatly depending on where you are in the universe. Cheers, Nigel

It will vary depending on where you are on earth and at what altitude, but when we have a huge variation on the specified density, who cares?

A pedant replies: No, it doesn't. Newtons and kilograms are arbitrary units. Note that I defined the conversion in terms of kgf, not kg. kg are units of mass, which are universal. Newtons are arbitrarily assigned to kg mass on Earth. The same principle applied on another planet wouldn't be Newtons. But Newtons on Mars are still Newtons. They're not very useful there, that's all.

thanks guys, not sure. Its for my course at uni, and I was stuck on this question for homework. found this useful website and hopefully is right Convert kilonewton to kilogram-force - Conversion of Measurement Units