01
Monthly contribution
The deposit stays level in dollar terms for the whole period. It never rises with pay or with prices, so a deposit made in year twenty does less work than the same amount in year one.
01Methodology
One compounding model drives every figure on this site. It is an educational illustration of how regular contributions and an assumed return may interact over a long horizon. It is not a prediction, a quote, or a guarantee.
Nothing you type leaves your browser. No account, email address, or personal data is required to run a projection.
Balance(n) = Balance(n−1) × (1 + i) + Contribution
Here i is the monthly rate, taken as the assumed annual return divided by twelve, and n counts the months from today until your retirement age.
The chart then splits the result into two bands: the money contributed, and the growth that accumulates on top of it. Comparing the two bands is often the most useful part of the estimate.
| Input | Treatment |
|---|---|
| Contribution | Fixed monthly amount, no increases |
| Return | Same rate in every year1 |
| Fees and taxes | Not deducted2 |
| Inflation | Not applied to results2 |
1 Real portfolios vary year to year. 2 See the full list in assumptions detail and the limitations disclaimer.
Test several rates and contribution levels in the scenario matrix to see how sensitive a long horizon can be.
Assumptions
Every figure you see here comes from a short list of fixed settings. They are listed below so you can judge how closely each one matches your own situation.
The deposit stays level in dollar terms for the whole period. It never rises with pay or with prices, so a deposit made in year twenty does less work than the same amount in year one.
A single annual rate is applied in equal monthly steps. Real markets do not deliver returns in that order, and a poor stretch early in the period costs more than the same stretch near the end.
Balances are shown in nominal dollars. Nothing is discounted back to today's purchasing power, so a large end figure will feel smaller than it looks.
No fund expense ratios, advisory charges, trading costs, or tax on growth are subtracted. Contributions are treated as money you have already paid tax on.
Deposits are credited at the start of each month, which gives each one slightly more time to compound than a deposit made at month end.
| Assumption | Held at | Effect on results |
|---|---|---|
| Contribution | Level, fixed dollars | Raises or lowers the total in a straight line |
| Annual return | One constant rate | Largest single lever on long-run balances |
| Inflation | Zero | Figures are nominal, not today's dollars |
| Fees and taxes | Zero | A funded account would give back some growth |
| Deposit timing | Start of month | Small lift compared with month-end deposits |
Change one setting at a time and the movement in the end balance belongs to that setting alone. Try a few rates side by side on the scenario matrix, read why the early years carry the most weight in compounding basics, or review the full statement of limits of the model.
04 — Limitations
The projection is an educational illustration built from one fixed set of assumptions. It is not a forecast, a quote, or a promise of any future balance.
Read this next to the assumptions detail before you draw conclusions from any figure.
Each scenario applies one steady annual return across the whole period. Real markets deliver uneven sequences of gains and losses, and a poor stretch early in retirement can reduce sustainable income far more than a flat average suggests.
The maths leaves out fund expense ratios, advisory fees, trading costs, and every form of taxation. Amounts appear without adjustment for inflation over the accumulation period.
Monthly contributions stay identical for the full timeline. There is no allowance for raises, career breaks, employer match changes, catch-up contributions after 50, or a missed payment.
Nothing on this page is investment, tax, or legal advice, and no result should be read as a recommendation. Your income, obligations, and goals are specific to you.
Output depends entirely on what you type in and the return you assume. Change the monthly amount or the assumed rate and the projection moves with it.
Talk to a qualified financial professional before acting on any projection. Full terms are set out in our Financial Disclaimer.