How many letters does the top answer for “an approximate calculation of quantity or degree or worth” have?

The most common answer is approximation (13 letters).

Crossword clue: an approximate calculation of quantity or degree or worth

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

approximation 13 letters wn-def

an approximate calculation of quantity or degree or worth

estimate 8 letters wn-def

judge tentatively or form an estimate of (quantities or time)