Old handbook of tables giving precalculated values (5,8)

I believe the answer is:

ready reckoner

(Other definitions for ready reckoner that I've seen before include "Calculating aid" , "I've done your sums for you" , "Tables of standard numerical calculations" , "Calculation aid" , "Book of calculation aids" .)

I've seen this clue in The Guardian.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.