Hello there. I would like to calculate the Time of Arrival/Estimate time of arrival of bus from point a to point b. I have the longitude, latitude, speed and time from tinygps library.. But i dont know the exact formula the perform the calculation.

time = speed / distance

speed = distance / time

distance = time * speed

I would like to calculate the Time of Arrival/Estimate time of arrival of bus from point a to point b.

You will need the path length and the average speed of the bus along each of the legs.

What will you be using as a route planner?

If you know lat/long and speed then search the internet for Great Circle calculations. Then you will know the shortest distance between the two points. But roads don't follow shortest distance and then there's traffic lights / junctions / bus stops etc to factor in. All the best!

Also see GPS distance calculation - Project Guidance - Arduino Forum