Equivalent RSA modulus for NIST P-192 and P-521 elliptic curves At www.keylength.com, I found the following table of ECC field size and the corresponding RSA modulus recommended by NIST. 

ECC Modulus  RSA Prime Size

160             1024

224             2048

256             3072

384             7680

512             15360

But NIST proposed P-192, P-224, P-256, P-384, P-521 curves. May I know what is equivalent RSA modulus for P-192 and P-521 curves?
Security strength of RSA in relation with the modulus size outlines the formula that is used for the strength of an RSA key (as a function of the size of the modulus).

For ECC it's a simpler "the prime field size / 2".

So ECC-192 => 96 bits of security.  $\sqrt[0.43]{96 / 4}$ = $\sqrt[0.43]{24}$ = $1621$, with $1624$ being the next highest number divisible by 8.

ECC-521 => 260.5 bits of security.  $\sqrt[0.43]{260.5 / 4}$ = $\sqrt[0.43]{65.125}$ = $16520.3$, making $16528$ the equivalent, which is beyond most systems' maximum of 16384.