Synonyms for Reckon:

n.

suspect, be a great/firm believer in something, recognize. tell, incline, adhere to, have a mind of your own, know best. prove, reason, add up. precise, set, place, put. perspective, esteem. belief, assume, posit, postulate, premise. trust, believe in. compute (noun)
study at calculate.

v.

add up; evaluate (verb)
rate, approximate, figure, appraise, count, view, esteem, judge, regard, place, compute, total, consider, tally, guess, enumerate, sum, cipher, estimate, gauge, put, surmise, calculate, account.
cognition (verb)
count.

Other synonyms:

believe in, incline, add up. recognize, adhere to, postulate, trust. posit. put, esteem. assume. tell. set. add
sum.
add up
total.
believe
view, suppose.
calculate
tell, multiply.
gauge
gauge.
suppose
posit.

Usage examples for reckon

  1. How far away d'you reckon it is? – In the Musgrave Ranges by Jim Bushman
  2. " I reckon replied Nichol, anxiously. – Taken Alive by E. P. Roe
  3. I reckon not, ma'am. – 'Firebrand' Trevison by Charles Alden Seltzer