How the retirement savings calculator works
The chain, in order
Target income − other income = the gap the portfolio funds. Gap × 12 ÷ withdrawal rate = nest egg needed. Current savings grow at your return; contributions must fill what remains, solved backwards into a monthly payment. Every link is visible — and every link is negotiable: income target, claiming strategy, return, rate, and date.
Why the withdrawal rate is a lever worth respecting
Dropping from 4% to 3.5% raises the required egg ~14% — significant, but often cheaper than five extra working years. Conversely, a pension-heavy household can justify 4.5–5% on the gap. The rate is not a universal constant; it is priced against your horizon and flexibility.
When the monthly number is impossible
The honest responses, in order of typical impact: extend the date (each extra year adds contributions AND removes a withdrawal year — double-barreled), trim the target (spending needs usually fall 20% from peak-career), exploit the match and tax-advantaged space first, and grow income. What does not work: hoping the return assumption rescues an unaffordable plan.