Gatwick to Heathrow

National Express coach

https://www.nationalexpress.com/en/airports/heathrow/gatwick-to-heathrow

That question is usually asked by someone who is flying into one of the airports, and intends to fly out of the other airport on the same day.
In which case the answer is: Don't do this unless you have no alternative and have a large number of hours to spend. You need to allow for:

• Your incoming flight being late
• Landing and taxiing
• Walking through long corridors (both Gatwick and Heathrow are good at this)
• Delays at Immigration (30-60 minutes not unusual)
• Picking up luggage and walking through customs
• Exiting and finding the bus
• Bus trip - nominally 1h 5 mins, unless it is a bad day on the M25
• Whatever minimum check-in time applies for your second flight.

A pre-booked private taxi will be no quicker, it still has to take the same route along the M25.

Thanks for the info; we are actually flying in to Gatwick Saturday night and leaving from Heathrow Sunday afternoon so time wise we will be ok.

we are actually flying in to Gatwick Saturday night and leaving from Heathrow Sunday afternoon

In that case, I suggest you hop a Gatwick Express train to London Victoria ( https://www.gatwickexpress.com/ ). Last train out of Gatwick Airport 23:21 on a Saturday, arrive London Victoria 23:55. Find a hotel within staggering distance of Victoria station. Then you have a few hours Sunday morning in London before catching a tube to Heathrow.
Much better than an airport hotel.

We've already booked and paid for a hotel at Gatwick. Thanks everyone for your input.

oh that's a shame.

How early is your Heathrow flight?

Are going elsewhere in Europe or long distance?

HI Nigel - our flight leaves at 4:10pm. We are heading back to the US after our 3 week trip in Europe.

Regarding the National Express coaches - we are staying at the Sofitel at the North Terminal at Gatwick. Anyone know the distance to the departure point? Trying to figure out when we should leave the hotel to meet our coach.

I've stayed at the Sofitel there and enjoyed it quite a lot. I hope your rate includes their breakfast.

The coach pick up/drop off is right outside the North terminal (or ot was the last time I used it). The Sofitel is connected to the terminal by a walkway at most a 5 min walk. The hotel will confirm if the pick up is the same place.