How to calculate the size of object?

Hi Jayant

Most records are 2KB, see the list below for exceptions..

Document storage is separate from data storage and counts at the actual size of the uploaded document.

For up to date figures on your company's use of storage please refer to:

Setup | Data Management | Storage Usage

Setup> Administration> Data> Storage Usage

For Leads,Contacts,Accounts,Opportunities,Forecasts,Events,Tasks,Cases ,Case Team Member,Solutions,Notes,Custom Reports,Contracts,Google Docs,Quotes,Custom Objects,Quote Template Rich Text Data it is-- 2KB
For Person Accounts,Articles it is- 4KB
For Campaigns - 8KB
For Campaign Members – 1KB
Email Message - This is dependent upon the content of the messages, a 100kb email message takes 100kb of data storage space.  Text only emails will take less than HTML due to only being the body text and not the html code and text version as well.

NOTE ABOUT PERSON ACCOUNTS
Person Accounts consume a record in both the Account and Contact objects. Each record allocates 2KB, so each Person Account record will require 4KB of storage space.

As an example, 500,000 person accounts will require around 2GB of storage.
Storage needed = (500000 X 4KB)/1024 = 1953.125 MB which when further divided by 1024 = 1.9073 GB which is around 2GB.

Images from Rich Text Fields are stored in file storage area.

Thanks