London to Windsor Castle by bus
Getting to Windsor from London is easy. There's a good bus service to Windsor that is probably the best option as the same service also connects Windsor Castle with Legoland Windsor. Regular trains from central London mean you've got a choice of transportation options and good connections to other destinations in the Southeast as well. Use these information resources to consider how you'll go and to plan your trip.
Green Line Service No. 702 is probably the most comfortable way to get to Windsor for the Castle and for Legoland, especially if you have kids in tow. Frequent buses leave from Victoria Colonnades, near London Victoria Coach Station roughly every half hour during the day. The journey takes about an hour.
The bus companies that run this service have been playing musical chairs in recent years and their online information has not always kept up. The main thing you need to know is that as of this writing - in December 2015, First Berkshire & The Thames Valley operate the service.
Ticket prices are not currently available online but the company does answer its telephone pretty promptly. Currently, adult one way tickets between London and Windsor Castle cost £10. Same day round trip tickets cost £15. Child, student and senior citizen tickets are available. Single and day-return (one day round trip) tickets are only available for cash from the bus driver.
UK Travel TipThe Legoland connection - There's probably too much to see and do at both Windsor Castle and Legoland Windsor to combine both in one day trip. But if you are staying at the family-friendly Legoland Resort the same Number 702 bus service will ferry you between the main entrance of Legoland Windsor and Windsor castle, The one-way adult fare is £4.20 and a day-return ticket is £6.20 (in 2016). Buy your ticket with cash from the bus driver.
Southwest Trains operate a direct service to Windsor & Eton Riverside Station from London Waterloo Station every half hour throughout the day (hourly on Sundays). The journey takes about an hour and round trip fares start at £11.70/$18.40 in 2015.
First Great Western run a faster, more frequent service to Windsor & Eton Central Station from Paddington Station, every 10 to 15 minutes throughout the day. The journey takes between 30 and 40 minutes but involves changing trains at Slough. Round trip tickets start at £10.40/$16.35.
Either station is a less than 10 minute walk so your travel choice would probably depend on whether you are closer to Paddington or Waterloo at the start of your trip.
UK Travel Tip Advance fares between London and Windsor are no cheaper than tickets purchased on the day of travel. But check the train and coach companies for special deals that may include entrance to the castle or other offers.
Windsor is 25 miles west of Central London via the M4 motorway. Leave the M4 at Junction 6 and follow signs into Windsor center. It takes about 45 minutes to drive. Parking throughout Windsor is controlled and relatively expensive. If visiting the Castle, use the Long Term parking. It may involve a 20 minute walk but it costs about a third of the cost of short term parking in Windsor center. An even better option is to use the Park and Ride services at Legoland Windsor or Windsor Home Park. There is a small charge for bus fare. The parking at Legoland is free. There is "pay and display" parking at Windsor Home Park.