Brown, Driver & Briggs (A Hebrew and English Lexicon of the Old Testament, based on the Lexicon of William Gesenius . . . first edition, page 1045) says on the word translated thinketh in the King James Version, “calculate, reckon . . . put a value on, estimate . . . Pr 23:7 as he calculated in his soul, so he is . . . as one who calculates . . .”

Commentaries

Commenting of the Revised Standard Version of the first part of verse 7 (one who is inwardly reckoning), Edgar Jones (Proverbs and Ecclesiastes, The Torch Bible Commentaries Series, page 191) says, “The text is uncertain but this sense is likely.”

Derick Kidner (Tyndale Old Testament Commentary Series, page 151) puts it this way, “. . . one’s grudging host . . . doing mental arithmetic . . . with every dish.” Kidner prefers the Revised Version rendering reckoneth to the King James Version thinketh. He says it is a rare word and that modern Hebrew supports reckons and that this has now been confirmed by Ugaritic (an ancient language closely related to Hebrew, evidence of which was first found by archaeologists in 1929).

David A. Hubbard (Proverbs, The Communicator’s Bible Commentary Series, page 358-359) says, “ ‘Thinks’ may mean ‘calculate’ or ‘estimate’ as though the bitter man were inwardly . . . calculating the food consumed and the time wasted. His ‘heart’ is not at all in his hospitality . . . The tiniest ‘morsel’ . . . eaten under such emotional duress will make one sick, figuratively, if not literally. . . . The Greek translation is more graphic . . . It likens the bad experience to swallowing a hair (Heb. ‘hair’ and ‘thinks’ in this text have the same consonants) . . .”

Jamieson; Fausset & Brown (Commentary Critical and Explanatory on the Whole Bible – Unabridged) says the word translated thinketh in the King James Version “means primarily to divide; hence, to decide, or estimate; and the noun a measure. He estimates his meats, and the cost of the entertainment, more than he does you; and is ill at ease if you eat much of his food. Eat and drink, saith he . . . but his heart is not with thee. He hospitably urges you to eat, but if you do, he will dislike you the more.

A. Cohen (Proverbs with Hebrew Text . . ., Soncino Books of the Bible Series, page 153) comments, “A generous host gives unstintingly to his guest and does not calculate what it costs him; but a miserly host resembles a man who estimates the amount involved in the transaction. Although he extends a cordial invitation to his guest to eat and drink, his heart is not in his words because he is worrying over the outlay.”

Other Commentaries on this verse:

Ellicott’s Commentary for English Readers
“He is not really friendly and hospitable, as his words would imply, but he grudges every morsel thou takest, calculating its cost.”

Matthew Poole’s Commentary
“. . . you are not to judge of him by his words, for so he professeth kindness, as it follows; but by the constant temper of his mind, which he hath fully discovered to all that know him by the course of his life.  . . . he hath no sincere kindness to thee, but inwardly grudgeth thee that which he outwardly offers to thee.”

Cambridge Bible for Schools and Colleges
“Not by his liberal words, “eat and drink,” but by the mercenary reckoning of his heart, which is calculating meantime and grudging the cost, is he to be estimated.”

Pulpit Commentary
“. . .  the clause is best rendered, For as one that calculates with himself, so is he. The meaning is that this niggardly host watches every morsel which his guest eats, and grudges what he appears to offer so liberally. . . . He professes to make you welcome, and with seeming cordiality invites you to partake of the food upon his table. But his heart is not with thee. He is not glad to see you enjoy yourself, and his pressing invitation is empty verbiage with no heart in it.”

Kretzmann’s Popular Commentary
“. . . his true nature does not appear on the outside, but his calculating meanness counts every bite his guest takes. Eat and drink, saith he to thee, with apparent politeness and cordial hospitality; but his heart is not with thee, he is not sincere, it is all sham and deceit, planned with selfish calculation.”