Looking for some simple models using basic maths but considering a number of factors. Was about to mock this up in a spreadsheet but is there anything online that already works?

Simplified Variables: -% portfolio fixed income / % cash / % equities -average returns in past 10 years on those above -> expected average future returns -average inflation over past 10 years -> expected average future inflation -average age of retirement / average number of years working -average income year on year -year on year defined contribution + extra contribution from state / tax ....

Ignoring all politics, I don't dream of retiring but the economy I participate in is driven in part by retirement consumption (or held back by unfunded pension liabilities depending on your perspective).

When I've done this in the past on the back of an envelope I came to the conclusion that roughly top 5% of earners could expect to retire on average income at 65 years old.

Comfortable retirement might have been a blip in human history.