Investment planner
Set a target amount and a horizon to solve for the monthly contribution, lump sum or annual return you need, with inflation adjustment and yearly contribution growth.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Plan inputs
Interest compounds monthly, the contribution is recalculated once a year by the growth rate, and the real value is deflated by the inflation rate.
Plan result
1,000,000.00+0.00655,931.13344,068.87744,093.911.5246 ×This tool is offline and does not forecast markets. The conclusion assumes a constant annual return of 8%; if the actual return shifts by one percentage point (7.00% – 9.00%), the final value lands roughly between 946,097.61 and 1,057,766.99.
Yearly plan
| Year | Contributed | Interest | Balance | Invested to date | Real value |
|---|---|---|---|---|---|
| 1 | 65,593.11 | 2,459.34 | 68,052.45 | 65,593.11 | 66,070.34 |
| 2 | 65,593.11 | 8,107.66 | 141,753.22 | 131,186.23 | 133,616.01 |
| 3 | 65,593.11 | 14,224.78 | 221,571.12 | 196,779.34 | 202,768.96 |
| 4 | 65,593.11 | 20,849.63 | 308,013.86 | 262,372.45 | 273,666.33 |
| 5 | 65,593.11 | 28,024.34 | 401,631.31 | 327,965.57 | 346,450.70 |
| 6 | 65,593.11 | 35,794.54 | 503,018.96 | 393,558.68 | 421,270.46 |
| 7 | 65,593.11 | 44,209.66 | 612,821.74 | 459,151.79 | 498,280.16 |
| 8 | 65,593.11 | 53,323.24 | 731,738.09 | 524,744.91 | 577,640.81 |
| 9 | 65,593.11 | 63,193.24 | 860,524.44 | 590,338.02 | 659,520.33 |
| 10 | 65,593.11 | 73,882.44 | 1,000,000.00 | 655,931.13 | 744,093.91 |
What this tool does
- Plan a savings goal: if you want 1,000,000 in 10 years, solve directly for the monthly contribution instead of guessing at numbers.
- Evaluate a lump sum: work out how much principal you need today so that an 8% annual return reaches the target by the deadline.
- Reverse-engineer the required return when the monthly contribution is already fixed, so you can judge whether the goal is realistic.
- Account for inflation and pay rises: deflate the result to today’s purchasing power and let the contribution grow by a fixed percentage each year.
Example
Input
Target 1000000, 10 years, expected annual return 8%, inflation 3%, initial principal 0, monthly contribution 0, yearly contribution growth 0, timing: end of month
Output
You need to invest 5,466.09 every month Projected value 1,000,000.00 Total invested 655,931.13 Total interest 344,068.87 Real purchasing power (after inflation) 744,093.91 Growth multiple 1.5246 ×
Interest compounds monthly at 8%/12 and contributions go in at the end of each month; the real value is deflated by 3% inflation over 10 years. Move the return one percentage point either way (7%–9%) and the final value lands between 946,097.61 and 1,057,766.99.
Frequently asked questions
Is this investment advice? Are the returns guaranteed?
No on both counts. The tool is pure arithmetic: whatever return you type in is what it uses. It is offline and does not forecast markets. Real returns fluctuate every year, so treat the output as a lower bound on how much you need to contribute, not as a promise.
How much difference does beginning-of-month vs end-of-month make?
Small but systematic: money contributed at the start of the month earns one extra month of interest, so the required contribution is slightly lower and the final value slightly higher. End of month matches the common "invest after payday" habit; pick beginning if your plan debits early.
Why does it say my target cannot be reached?
Because the bisection search stops at a monthly contribution of 100,000,000, or the required return falls outside the -50% to 300% search range. The usual causes are a term that is too short, a negative return, or an absurdly large target. Check the return and the term before raising the contribution.
What should I put in the yearly contribution growth field?
The percentage by which you expect to raise the monthly amount each year. If your salary grows 5% a year, enter 5: from year two you invest 5% more per month, and the year after that the increase stacks on top. Zero keeps the contribution flat, and negative values model a shrinking contribution.
What does the real purchasing power row mean?
It converts the closing balance back into today’s money using the inflation rate. At 3% inflation, 1,000,000 in ten years is worth 744,093.91 today, so inflation quietly eats about a quarter of it. To keep your purchasing power intact, raise the target by the same proportion.
Keywords：investment plannersavings goalmonthly contributionrequired returninflation投资规划定投计算理财目标通胀折算每月定投