It is a synonym for "assume"
Very formidable. A force to be reckoned with.
Era - A period of time as reckoned from a specific date serving as the basis of its chronological system.
thought or supposed
Reckoned.
Animal Atlas - 2004 Birds to be Reckoned With was released on: USA: 4 February 2011
She is an amazing person, and is a force to be reckoned with.
Beckoned, second
Biography - 1987 Mark Hamill A Force to be Reckoned With was released on: USA: 21 May 2002
Face Off - 2011 A Force to Be Reckoned With 3-1 was released on: USA: 21 August 2012
The phrase is actually "a force not to be reckoned with" and it means you need to steer clear of a person, organization, evilness or enemy. Here is a sample sentence. Adolf Hitler and Josef Stalin would kill people at will and wielded the power with such force and evilness that people would do everything they could to avoid being killed by them. They were "forces not to be reckoned with" because they were too dangerous.
Hungary is generally reckoned a part of Central Europe.
A force to be reckoned with means someone or something that is powerful, influential, or capable of making a significant impact or impression. It suggests that the individual or entity should not be underestimated or taken lightly.