Reckoner

n.

1.

One who reckons or computes; also, a book of calculations, tables, etc., to assist in reckoning. Reckoners without their host must reckon twice. - Camden.

Noun	1.	reckoner - an expert at calculation (or at operating calculating machines) Synonyms: estimator, figurer, calculator, computer
	2.	reckoner - a handbook of tables used to facilitate computation Synonyms: ready reckoner

actuary, adder, calculate, calculator, cipher, compute, computer, cypher, estimator, expert, figure, figurer, number cruncher, reckon, statistician, subtracter, work out