CalculatorsInvestment calculator
Investment calculator
If you invest this amount and keep contributing, see what it could be worth over time, including the effect of fees.
Your plan
Tell us about your investment
An assumption for the calculator, not a guaranteed return.
Adjust assumptions (fees, inflation)
The percentage of your investment charged in fees each year.
Show the projected value in today's money alongside the headline figure.
Projected value after 10 years
£37,803
At a 5% assumed annual return, your £29,000 of contributions could grow to approximately £37,803 over 10 years. With a 0.5% annual fee, your projected value is approximately £1,214 lower over this period than it would be fee-free.
- Term
- 10 years
- Invested
- £29,000
- Estimated growth
- £8,803
- Projected value
- £37,803
Impact of fees
At a 0.5% annual fee, this is what the fee is estimated to cost: not just what's deducted, but the growth that money would otherwise have gone on to earn.
- Projected value before fees
- £39,017
- Projected value after fees
- £37,803
- Estimated impact of fees
- £1,214
Year-by-year projection
| Year | Contributions | Growth | Balance |
|---|---|---|---|
| 1 | £2,400.00 | £272.59 | £7,672.59 |
| 2 | £2,400.00 | £392.18 | £10,464.77 |
| 3 | £2,400.00 | £517.13 | £13,381.90 |
| 4 | £2,400.00 | £647.68 | £16,429.58 |
| 5 | £2,400.00 | £784.06 | £19,613.64 |
| 6 | £2,400.00 | £926.55 | £22,940.19 |
How it works
How investment growth works
This calculator takes what you're starting with, adds whatever you plan to contribute regularly, and applies your assumed annual return month by month for however long you're investing, so you can see how a projected value builds up over time, not just what it might end at.
It's built around a different question from the compound interest and savings calculators: not "how does compounding work" or "what could a savings account be worth," but "if I invest this and keep contributing, what could it grow to?" That includes the things that make investing different from saving: fees, and returns that are never guaranteed.
Show the technical explanation
Calcular simulates your balance one month at a time. Each month, growth is applied to the balance carried over from the previous month, any fee is deducted from the grown balance, and then — if one is due — that month's contribution is added. A contribution never earns growth or pays a fee in the month it's paid in; it starts from the next month, the same ordinary-annuity convention used throughout Calcular.
Your "expected annual return" is treated as a compound annual growth rate (CAGR) — the standard way an average yearly return is quoted — and converted to a monthly rate geometrically: monthly rate = (1 + expected return)^(1/12) − 1. That's deliberately not the same calculation as the Savings calculator's AER conversion: AER is a regulated figure a bank is required to quote, while an expected return is your own forward-looking assumption. Both use the same underlying maths for the same reason: dividing an annual rate by 12 and compounding it monthly would overstate the annual figure you actually entered.
The monthly-equivalent rate derived from your expected annual return:
monthly rate = (1 + expected return) ^ (1/12) − 1
Compounding that monthly rate for 12 months reproduces the annual return you entered exactly.
Saving toward a shorter-term goal rather than investing? Use the savings calculator →
An important distinction
Investment returns aren't interest
A savings account pays interest at a rate the provider sets and (usually) honours for as long as you hold the account. An investment doesn't work that way: its value moves with the market it's invested in, which can rise, fall, or do nothing for long stretches. There's no equivalent of an AER a provider promises you.
That's why this calculator asks for an "expected annual return" rather than an interest rate: it's a single assumption standing in for what could be an uneven, unpredictable sequence of real returns. Treat the result as an illustration of what a steady average might produce, not a forecast of what will actually happen.
Fees
How fees affect investment growth
Investment platforms, funds, and advisers typically charge an ongoing percentage of what you hold with them each year. That charge doesn't just reduce your balance by that percentage once. Because it's taken from money that would otherwise stay invested and keep growing, its real cost compounds over time, the same way your returns do.
This calculator applies your annual fee every month, as a percentage of your balance at the time — consistent with how most platform and fund charges actually work — rather than subtracting one lump sum at the end. To show what that costs you, it runs the same projection twice: once with the fee, once without, and compares them.
Show the technical detail
The fee is converted to a monthly factor the same geometric way returns are: monthlyFeeFactor = (1 − annual fee)^(1/12), applied to the balance immediately after that month's growth. "Projected value before fees" re-runs the same contributions and return assumption with no fee at all. "Estimated impact of fees" is the difference between the two final values: not simply the fees taken out, but that amount plus all the growth those deducted amounts would have gone on to earn. It will always be larger than the raw amount deducted in fees, which is exactly the point: fees cost more over time than their headline percentage suggests.
The monthly-equivalent charge factor derived from your annual fee:
monthly fee factor = (1 − annual fee) ^ (1/12)
Applied to the balance straight after that month's growth, before that month's contribution is added.
Inflation
Inflation and your investments
A projected value in tomorrow's pounds isn't worth the same as that many pounds today. Prices tend to rise over time, so the same amount buys less in the future. This calculator's inflation adjustment is optional and off by default; when you turn it on, it shows a second figure — what your projected value would be worth in today's money — alongside the original nominal figure, never instead of it.
The default assumption, 2%, is the Bank of England's inflation target for UK consumer prices (CPI), a policy goal, not a prediction of what inflation will actually average over your investment period. You can change it to whatever you think is more realistic.
Worked example
£5,000 to start, £200 a month, 5% expected return, 0.5% fee
Say you invest £5,000, add £200 every month, assume a 5% annual return, and pay a 0.5% annual fee, for 10 years.
- You invest
- £29,000.00
- Estimated growth
- £8,803.12
- Projected value
- £37,803.12
- Before fees
- £39,017.11
- After fees
- £37,803.12
- Estimated impact of fees
- £1,213.98
The 0.5% annual fee is estimated to cost about £1,214 over the 10 years. That's more than the roughly £1,010 actually deducted, because that deducted money would otherwise have stayed invested and kept growing.
Good to know
What this calculator does, and its limits
What it does
Simulates a projected investment value month by month, using the starting amount, contributions, expected annual return and annual fee you enter, so you can see how a projected balance and its make-up of contributions vs. estimated growth change over time — and, if you turn on inflation, what that might be worth in today's money.
Assumptions
- Assumes a constant expected annual return for the whole period. Real investment returns vary from year to year, can be negative, and may differ substantially from any single assumption.
- Applies the annual fee every month as a percentage of your balance, consistent with how most platform and fund charges work.
- Treats the expected return as a total return: if you intend it to include reinvested dividends or distributions, they're assumed to already be built into the figure you entered. There's no separate dividend field.
- Doesn't include tax: Capital Gains Tax, dividend tax, ISA allowances, and pension tax relief are all outside what this calculator models.
- Assumes every contribution is paid in full, on time, with no withdrawals.
Not financial advice. This is a general information tool, not a personal recommendation, and it can't tell you what return to expect or whether an investment is right for you. Speak to a regulated financial adviser before making significant investment decisions.
FAQ
Common questions
How is investment growth calculated?
This calculator simulates your balance month by month: your expected annual return is converted to a monthly-equivalent rate and applied to the balance, any fee is deducted, and contributions are added afterwards. It's a deterministic projection based on the single return you enter, not a simulation of real, variable market behaviour.
What annual return should I use?
There's no single right answer. It depends on what you're invested in and the period you're looking at, and past performance doesn't guarantee future results. Rather than picking one figure and trusting it, it's worth trying a few different, reasonable assumptions and seeing how much the projected value changes.
Is a 5% return guaranteed?
No. 5% is simply this calculator's default starting point, not a prediction or a promise. Every expected return you enter here is an assumption you're choosing, not a rate any product owes you.
How do investment fees affect returns?
Fees reduce your balance every time they're charged, which means less of your money is left invested and growing afterwards. Over a long period, that compounds, so the true cost of a fee is usually larger than the fee percentage alone suggests. This calculator's "estimated impact of fees" figure captures that full effect, not just the amount deducted.
Does this calculator include inflation?
Only if you turn it on. By default, results are shown in nominal terms: future pounds, not adjusted for the falling purchasing power of money over time. Enabling the inflation toggle adds a second, "today's money" figure alongside the nominal one.
What does "today's money" mean?
It means your projected value adjusted for assumed inflation, so it reflects roughly what that amount would be able to buy at today's prices rather than its raw future pound value. It's shown alongside the nominal projection, never instead of it.
Does this calculator include tax?
No. Capital Gains Tax, dividend tax, ISA allowances, and pension tax relief are all outside what this calculator models, since they depend heavily on your personal circumstances and which account you invest through. The figures shown are before any tax you might owe.
Does this include dividends?
The expected annual return you enter is treated as a total return. If you intend it to include dividends or other distributions being reinvested, that's already accounted for in the figure you choose. There's no separate dividend field to fill in.
Can investments lose money?
Yes. Unlike a savings account, an investment's value can fall as well as rise, including below what you originally put in. This calculator allows a negative expected return specifically so you can see what that looks like in the projection.
Is this financial advice?
No. Calcular is a general information tool, not financial advice, and nothing here should be treated as a personal recommendation. It doesn't know your full financial situation, risk tolerance, tax position, or goals. If you're deciding where to invest a significant amount of money, it's worth speaking to a regulated financial adviser.
Keep exploring
Want to see what else your money could do?
Saving toward something shorter-term, or investing for retirement? These cover both.