Kiran,
This is platform specific. The 'show cry eli' command should be able to tell you that information for your specific platform:
Example:
Hardware Encryption : ACTIVE
Number of hardware crypto engines = 1
CryptoEngine NETGX details: state = Active
Capability : IPPCP, DES, 3DES, AES, IPv6, GDOI, FAILCLOSE
IPSec-Session : 0 active, 2400 max, 0 failed
Keep in mind that due to re-keying, you'll only be able to get about 1/2 your limit (because you will have both the old IPSEC SA and the new IPSEC SA for a short period of time, until the old SA expires).
--Jason