https://privatekeys.pw/calc

First go to the page above, paste 500 keys or less at a time then hit "priv --> addr_c" for compressed, and "priv --> addr_u" for uncompressed, rinse and repeat. After that you could check other suggested tools to check for balance.

Please note that you should be offline while on that page, after you are done you should delete all cookies, site data etc, or better yet use a different browser then uninstall it after you are done.