What is the ISD code from India to US?

The telephone country code for the United States (as well as Canada and 18 miscellaneous islands in or near the Caribbean) is +1.

As dialed from India, that is +1 on a mobile or 00 1 on a landline or fax.

You then need the area code (always 3 digits) and subscriber number (always 7 digits). For example, +1 212 555 0123.

(The plus sign means "insert your international access prefix here." From a GSM mobile phone, you can enter the number in full international format, starting with the plus sign. The most common prefix is 00, but North America (USA, Canada, etc.) uses 011, Japan uses 010, Australia uses 0011, and many other countries use different prefixes.)