Plan your retirement from four angles: how large a nest egg you'll need, the monthly savings to reach a target, the sustainable withdrawal your savings can support, and how long a fixed pot of money will last. Switch tabs to ask each question with its own inputs.
Formula
Retirement planning combines growth before retirement with spending after it.
Savings grow to: FV = balance × (1 + r)^years
Contributions: FV of a (growing) annuity of your yearly deposits
Nest egg needed: present value of a withdrawal that starts at your
first retirement year and grows with inflation, while
the balance keeps earning the return r
How long it lasts: months = −ln(1 − balance × rₘ / withdrawal) / ln(1 + rₘ)
Where r is the annual return and rₘ = r / 12 is the monthly return.
The three rules of thumb
| Rule | What it says |
|---|---|
| 10% Rule | Save 10–15% of income every year |
| 80% Rule | Plan to need ~70–80% of pre-retirement income |
| 4% Rule | Nest egg ≈ annual retirement spending ÷ 4% |
Examples
How much do I need? (age 35, retire at 67)
A 35-year-old earning $70,000 (rising 3%/yr), needing 75% of their final salary, with $30,000 saved and contributing 10% of income at a 6% return and 3% inflation, needs roughly $1.9 million at retirement — and is projected to have about $1.1 million, a shortfall to close by saving more or retiring later.
How long will it last? ($500,000 at $3,000/mo)
A $500,000 balance earning 6% while withdrawing $3,000 a month lasts about 30 years. Drop the withdrawal to $2,000 a month and the 6% return more than covers it, so the balance lasts indefinitely.