How to determine the crawl budget?

The number of pages Google crawls, your 'budget', is generally determined by the size of your site, the 'health' of your site (how many errors Google encounters) and the number of links to your site.

Divide the number of pages by the "average crawl per day". If you end up with numbers higher than ~10 (so you have 10x more pages than Google crawls per day), you should probably optimize your crawl budget. If you end up with a number below 3, you can definitely go read something else.

Go to "Settings" -> "Crawl stats" and write down the average pages crawled per day. Divide the number of pages by the "Average crawled per day" number. You should probably optimize your crawl budget if you end up with a number higher than ~10 (so you have 10x more pages than what Google crawls daily).

Go into Google Search Console. Go to "Settings" -> "Crawl stats" and calculate the average pages crawled per day. Divide the number of pages by the "Average crawled per day" number.