Retirement planning fails in one predictable way: people underestimate how much their lifestyle will cost decades from now. This calculator attacks that blind spot directly. It starts with your Current Monthly Expenses ($), compounds them by the Annual Inflation Rate (%) over the years between your Current Age and Retirement Age, and arrives at the monthly income your future self will actually need. Then it prices that income stream as a lump sum — the Target Retirement Savings ($) — using your Expected Return Post-retirement (%), and finally solves for the Required Monthly Savings ($) that, growing at your Expected Return Pre-retirement (%), builds exactly that corpus.

A 30-year-old spending $4,000 a month, retiring at 60 with 6% inflation: monthly needs at retirement swell to about $23,000. Funding 25 years of that at an 8% post-retirement return demands a corpus near $5.9 million — and building it at 12% pre-retirement requires saving roughly $3,400 every month starting now. The Years to Retirement versus Years in Retirement split shows why starting late is so punishing.

The numbers are meant to jolt, not depress. Every year you delay, the monthly requirement climbs; every year you start early, compounding quietly does your heaviest lifting.

With the pre-filled defaults — Current Age (years) 30, Retirement Age (years) 65, Life Expectancy (years) 85, Current Monthly Expenses ($) 5,000, Annual Inflation Rate (%) 3, Expected Return Pre-retirement (%) 8, Expected Return Post-retirement (%) 5 — the Retirement Calculator returns Years to Retirement 35, Years in Retirement 20, Monthly Expenses at Retirement ($) 14,069.31, Target Retirement Savings ($) 2,781,137.72, Required Monthly Savings ($) 1,204.39. Change any input and those results update instantly, so you can see exactly how each number you enter moves the answer.