http://networthify.com/earlyretirement
Also, the author's example was a household that makes $100,000 annually and saves 10%. They must work 52 years to save the $2.3 million needed to retire.
If they increased their savings rate to 50% they could retire after 17 years and would only need $1.3 million.
If they increased their savings rate to 80% they could retire after 5.6 years of work and would only need to save $544,000.
Also, with the defaults it has (5% above-inflation profit and 4% withdrawal rate), it results in the savings that never end but continue growing at about 1% per year, which is an overshoot for someone who just wants to retire, not leave a huge legacy.
That calculator intentionally assumes "forever", which gives you a safe margin for error; that doesn't actually change the amount you need to save by very much. Also, as the URL suggests, that calculator aims particularly at people trying to save heavily and retire early, and given that, the difference between "save enough for 50-60 years of retirement" and "save enough for an indefinite retirement" doesn't add up to very much.
> Also, with the defaults it has (5% above-inflation profit and 4% withdrawal rate), it results in the savings that never end but continue growing at about 1% per year
Again, margin for error. If you count on withdrawing exactly what you can get from your investments, then whenever those investments don't do so well in a particular year, you'd get significantly less income than you planned on.
And yes, i didn't use 'inflation' at all. Prosperity and 'good living standards' is relative. If an old guy started saving in 1960 when he was 25 and he's now 77, what was good living standard then is now poverty. I used nominal GDP per capita to 'deflate' my net worth over years, data from www.measuringworth.com.
Another reason why i don't recommend using 'inflation' is that everyone has different consumer bundle so his inflation is different from the CPI. And the measurement of inflation is overally broken, i don't trust it, and believe it is meaningless. As long as you don't face risk of starvation, there is little importance on how much stuff you can buy, how you do vs others is important.