I don't have much knowledge on these music exams. I wanted to know that if I start learning Piano from scratch, how long will it take me to reach Grade 5 in ABRSM or Trinity exam? I tried looking for help over a few websites, but couldn't find much. Your answers and views would be much appreciated.
The reason you can't find a answer is that there isn't a definitive one. There are so many factors involved. How much time will you practise per day? How much do you know about music already? Can you read music? How much natural musical ability do you have? How often and for how long will you have lessons? How coordinated are you (can you do different things with your right and left hands?) It's like learning to drive - some people don't need that many lessons, some people need loads. You won't know until you start.
I completely agree with Tisy. An additional factor is also whether you/the child is happy just to pass, or whether you are looking to get a distinction at each level.
Just for some comparison though....
Dd started playing the piano in September 2012 when she was 7. She did grade 1 piano in December 2013 and got a distinction. She did grade 2 piano in June 2014 and we have yet to get the result. I think she will get a merit rather than distinction as she only started preparing the pieces in April, so it was probably a bit quick really. I think she will do a grade a year moving forward as the "steps" between the grades seem to get quite big from this point on. However, that's really only a guess as I have no idea how she will get on!
Dd is very musical (as I am), so I am able to support her practising which I think makes a big difference at the early stages.