Definition of reckon :
1. To charge, attribute, or adjudge to one, as having a certain quality or value.
2. To come to an accounting; to make up accounts; to settle; to examine and strike the balance of debt and credit; to adjust relations of desert or penalty.
3. To conclude, as by an enumeration and balancing of chances; hence, to think; to suppose; - followed by an objective clause; as, I reckon he won't try that again.
4. To count as in a number, rank, or series; to estimate by rank or quality; to place by estimation; to account; to esteem; to repute.
5. To count; to enumerate; to number; also, to compute; to calculate.
6. To make an enumeration or computation; to engage in numbering or computing.
envisage, betoken, predict, assure, cogitate, augur, moot, write in code, belief, go out, escort, run into, appear, encounter, watch, deem, fancy, perspective, deliberate, ensure, expect, pick up, speak up, conceive of, place, call back, cerebrate, hypothesize, theorize, view, reason, understand, exercise, discover, encipher, figure out, cipher, search, number, picture, theorise, set, deal, believe in, examine, solve, matter, attend, run across, look, cast, lick, work up, control, ascertain, inscribe, elaborate, hypothesise, image, front, recollect, look at, esteem, prefigure, pretend, depend, direct, portend, animadvert, puzzle out, go steady, precise, find out, posit, opine, go through, presage, venture, work out, hear, speak out, recall, premise, regard, await, bet, forecast, presuppose, construe, take care, learn, call up, speculate, aim, get wind, visualise, enter, play, hypothecate, auspicate, meet, visit, sound off, code, face, foretell, date, realize, debate, believe, see to it, conjecture, imagine, wager, work, study at calculate, envision, trust, foreshadow, assume, prognosticate, involve, count on, interpret, say, witness, see, conceive, put, come across, cypher, numerate, take, bode, find, omen, tell, check, realise, hazard, encrypt, remember, experience, take in, affect, wait, project, catch, seem, get word, get a line, insure, visualize, intend, turn over, sum up, retrieve, ideate, mean, postulate
calculate (part of speech: verb)
systematize, figure, calculate, rationalize, quantify, quantize, multiply, compute, count, think, plot, sum, gauge, conclude, suppose, value, consider, total, weigh, scheme, guess, schedule, assess, tally, determine, deduce, estimate, surmise, plan, approximate, presume, score, study, rate, rank, infer, measure, judge, account, evaluate, add, divide, program, triangulate, appraise, enumerate