Indeed the math did go over my head, too, but I'm actually going to sit down and do it as some stage as it (eventually) helps me get my head around things. However, from what I can understand so far: Let's say I save 800,000 in investment before retiring at 50 at which time I also have 200,000 lump sum value in my pension (because I won't still be paying into it if I've retired early). I then start taking how much I need to live on from the 800,000 investment. This means that this investment will start to decrease a bit because I'll be taking out say 40,000 and with the 4% rule only accruing 32,000. This means each year my 800,000 investment is decreasing by 8,000 because I'm withdrawing more than the interest I'm getting. If I do that for 12 years until the pension kicks in at 62 then I'm down 96,000 overall. However, at this time, my pension then kicks in so I won't need to over withdraw from either account because the pension will compensate for the 96,000 that I'm now down overall? I appreciate this is all very simplified and doesn't account for things like me becoming a part time model and uber driver or an incredible time with the markets meaning a 10% return on everything, but am I along the right track?