simple past tense and past participle of reckon with

Able to be reckoned or computed.

Too powerful or important to be ignored.

(historical) A printed book or table containing precalculated values, often multiples of given amounts. / A computer program which calculates values; an online calculator.

plural of ready reckoner

Alternative spelling of ready reckoner

(historical) A very early mechanical calculator (completed in 1694) invented by Gottfried Wilhelm Leibniz.

plural of stepped reckoner

A method of estimating the position of a ship or aircraft by applying estimates of the distance and direction travelled to a previously known position. In respect to ships/boats, it excludes the effect of wind and current on the vessel. Compare with estimated position. Abbreviation: DR

(idiomatic, uncommon, archaic) A (falsified) bill that is not itemised, and that is unjustifiably high. / (nautical) A false or incorrect reckoning of position.