aquilatar

Originally a jeweler's term for assaying gold or gems — determining their karat/purity — extended figuratively to carefully weighing, gauging, or assessing the true worth or quality of something abstract, like an argument or a person's character.

• El joyero aquilató el oro antes de comprarlo. — The jeweler assayed the gold before buying it.
• Es difícil aquilatar el verdadero valor de su aporte. — It's hard to gauge the true value of his contribution.
• Hay que aquilatar bien los pros y los contras antes de decidir. — You need to carefully weigh the pros and cons before deciding.

Using aquilatar for simple measuring or weighing of physical objects outside the jewelry context — for that, pesar or medir is what a native speaker reaches for; aquilatar is reserved for the more figurative, evaluative sense (or literal gemstone assaying).