Here are some informations I found on the magnetic field strength (also called "magnetic flux density" or "magnetic induction", commonly denoted as B and expressed in tesla or in gauss) of an average neodymium-iron-boron rare earth magnet.
"A modern neodymium-iron-boron (NIB) rare earth magnet has a strength of about 1.25 T." http://teslaradioconspiracy.blogspot.fr/2007/11/tesla-si-unit-of-magnetic-field.html
"1.25 T – magnetic field intensity at the surface of a neodymium magnet" http://en.wikipedia.org/wiki/Tesla_%28unit%29#Examples
"1.25 T – strength of a modern neodymium–iron–boron (Nd2Fe14B) rare earth magnet." http://en.wikipedia.org/wiki/Orders_of_magnitude_%28magnetic_field%29
"The magnetic field typically produced by rare-earth magnets can be in excess of 1.4 teslas, whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla." http://en.wikipedia.org/wiki/Rare-earth_magnet
Clearly, all of these sources agree that an average neodymium-iron-boron rare earth magnet has a magnetic field strength of about 1.25 T.
But here's the problem: I searched on every single possible websites for THE most powerful magnet that can be bought.
And THE most powerful magnet that can be bought is this one: http://www.kjmagnetics.com/proddetail.asp?prod=BZX0ZX0Y0-N52
It has dimensions of 4" x 4" x 2", a weight of 138.8 oz (3934 g) and a pull force of 1226.5 lbs.
And a magnetic field strength (surface field) of 4933 Gauss.
4933 G = 0.4933 T
Far from the value of 1.25 T that is supposed to be the magnetic field strength of just an average rare-earth magnet...
How is this possible?
And also, I found something else very intriguing: http://www.kjmagnetics.com/proddetail.asp?prod=BZX0Z0Y0-N52
This magnet has dimensions of 4" x 3" x 2", a weight of 104.1 oz (2950 g) and a pull force of 1013 lbs.
So this magnet is smaller, less heavy and less powerful than the previous magnet.
But it has a magnetic field strength (surface field) of 5336 G = 0.5336 T which is greater than the previous magnet!
Again, how is this possible?
Note: Both magnets are made of the same material (NdFeB, grade N52). Both magnets have the same magnetization direction (thru thickness). And both magnets have the same plating/coating (Ni-Cu-Ni, Nickel).