If you only need a very simple calculation, look for lightweight, free calculation plugins that don't require "pro" features.
There is no such thing as a "safe" nulled script. Every illegal download is a gamble where the house always wins—and the house is a hacker.
: Nulled scripts are a primary vector for malware, backdoors, and ransomware. Hackers use these to gain administrative access to your site [1, 3]. SEO Damage
Your website’s reputation and security are worth more than the price of a plugin license. Stay safe, stay updated, and keep your data secure by avoiding nulled scripts.