About Retirement Math
Retirement planning compresses to two questions: what will I have, and what will it pay me? The first is compounding arithmetic on your savings rate and timeline; the second is a withdrawal-rate judgment the industry has argued about for thirty years. This calculator answers both in one pass, with the argument's honest summary attached.
Enter your ages, current savings, monthly contribution, and assumed return. You get the projected nest egg at retirement and the annual/monthly income the 4% guideline implies — pre-tax, in future dollars, with the caveats that make the number useful rather than falsely precise.
Employer plan with matching? Project it specifically with the 401k Calculator.
Nest Egg, Then Income
Future value first, withdrawal guideline second:
Nest egg = current × (1+r)ⁿ + monthly × ((1+r)ⁿ − 1) ÷ r Income ≈ nest egg × 4% (year one; inflation-adjusted thereafter)
Worked example: age 30, $50,000 saved, $500/month at 7% until 65 → about $1.48M, suggesting ≈ $59,000/year ($4,900/month) by the 4% guideline. Delaying the start to 40 drops the nest egg to ~$680k and the income to ~$27k — the cost of a decade, made visible.
Monthly Savings → Retirement Income
From age 30 to 65 at 7%, no starting balance — nest egg and its 4% income (all computed by this calculator's formulas):
| Monthly saving | Nest egg at 65 | 4% income/yr | ≈ Monthly |
|---|---|---|---|
| $250 | $443,000 | $17,700 | $1,480 |
| $500 | $886,000 | $35,400 | $2,950 |
| $1,000 | $1,772,000 | $70,900 | $5,910 |
| $1,500 | $2,658,000 | $106,300 | $8,860 |
The table's quiet lesson: retirement income scales linearly with savings rate but exponentially with time — the age-30 saver's $500 beats the age-45 saver's $1,500.
The 4% Rule, Honestly
The guideline comes from studies of historical US portfolios (the Trinity study lineage): an initial 4% withdrawal, inflation-adjusted annually, survived every historical 30-year retirement in the data. Its honest limits: it's US-history-specific, assumes a balanced stock/bond mix, ignores fees and taxes, and 30 years may undershoot early retirees. Bad early-year markets (sequence risk) are its known failure mode.
Practice has evolved toward flexibility rather than a fixed rule: spending that flexes with markets, guardrail methods, and rates from 3.3% (pessimistic) to 5%+ (flexible spenders). And this calculator's scope is honest too — Social Security, pensions, and part-time income all ADD to the 4% figure, often substantially. Treat the output as the investment leg of a stool, not the whole seat.