Do I need a visa to visit USA from UK?
The United Kingdom is one of the 38 nations that have been admitted to the ESTA Visa Waiver Program of the USA. This means that citizens of the UK are exempt from having to apply for a visa for the USA if they have a valid ESTA permit.
If you are travelling from the UK to the US for a longer period than 90 days, planning to do active business or any other reason that refuses to issue an ESTA permit, you are required to apply for a visa at a US Embassy.
Tip: With a valid ESTA permit, you may travel 90 days at a time to the USA. Since an ESTA permit is usually valid for 2 years, you can travel to the USA for several times!