Planning to retire soon-ish so obviously considering this too.
The only way to make an individualised assessment is to go through all your income and expenditure for the last 12 months, then work out a monthly average.
It's a pain to do this, but you only need to do it once!
I found that it only took a couple of evenings with my bank account/credit card account open and a pen and paper - I sorted everything into categories - food, transport, etc.
You also need to consider what will change, e.g. are you planning to travel more, buy fewer clothes, etc.? Martin Lewis has a good expenditure calculator on his website.
So, exceptional expenses aside, I know pretty much exactly what I need to live on in retirement. Don't forget to factor in interest rates/rising prices!
For me, the current 'recommendations' are quite high, but they might be realistic for someone who is used to a foreign holiday every year, buying take-aways, etc.
So, message is - do your own projection, based your own information, not what someone else thinks you might be doing.