Investment Calculator
Project a portfolio with regular contributions, then strip out the two things that quietly take most of the upside: annual fees and inflation.
Investment Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: A $10,000 portfolio with $500 a month at 8% for 25 years grows to $548,914.96 gross. A 0.75% annual fee removes $66,548.36 of that, leaving $482,366.60 — and at 3% inflation the real purchasing power is $230,380.97 in today's money.
Formula
P = initial sum · C = monthly contribution · i = monthly return net of the fee · n = months. Real value divides the result by (1 + inflation)years.
Worked Example
- Net the fee off the return. 8% − 0.75% = 7.25%, or 0.0060417 a month.
- Grow the initial sum. $10,000 × (1.0060417)300 = $60,924.28.
- Grow the contribution stream. $500 a month for 300 months compounds to $421,442.32.
- Add them. $482,366.60 net of fees, against $548,914.96 with no fee at all.
- Discount for inflation. $482,366.60 ÷ (1.03)25 = $230,380.97 in today's purchasing power.
Analyst's note. Three-quarters of one per cent sounds negligible and costs $66,548.36 — 12.1% of the entire gross result — because the fee is levied on the balance every year, including on the growth it has already suppressed. Fee compounding is the mirror image of return compounding, and it is the only variable on this page you fully control.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Comparing two funds with different expense ratios
Run the projection twice, changing only the fee. The difference is the true lifetime cost of the more expensive fund, which is invariably far larger than the annual percentage suggests. Compare the underlying growth rates with the CAGR Calculator before assuming the pricier fund earns its fee.
Setting a realistic retirement contribution
Fix your horizon, then solve by trial for the contribution that reaches your target in today's money rather than nominal dollars. Cross-check the resulting income against the Retirement Calculator, which models the drawdown phase this tool does not.
Judging a lump sum against a contribution habit
The engine separates the two: here the initial $10,000 becomes $60,924.28 while the monthly habit becomes $421,442.32. Consistency usually beats the starting balance over long horizons. For a single sum with no contributions, the Future Value Calculator is the cleaner tool.
Methodology & Editorial Standards
Growth is computed with the standard future-value formula for a present sum plus an ordinary annuity, on a monthly grid, with contributions assumed at the end of each month. The fee is applied as a reduction to the annual return before conversion to a monthly rate, which is the conventional treatment for an expense ratio levied on assets. Gross and net are computed as two independent projections so the reported fee drag is a genuine difference. Real value discounts the nominal result at the stated inflation rate over the whole horizon. Returns are assumed constant; actual markets are not, and sequence-of-returns risk is not modelled. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Investment Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How much difference does a 0.75% fee really make?
On this projection, $66,548.36 — which is 12.1% of the entire gross result. The fee is charged on the whole balance every year, so it also removes the growth that money would have produced. Small percentages compound into very large sums.
Why is the real value so much lower than the projection?
Because $482,366.60 in 25 years buys what $230,380.97 buys today at 3% inflation. Nominal projections flatter every long-horizon plan. Judge a target in today's money and let the nominal figure be whatever it needs to be.
What return should I assume?
Be conservative. Long-run global equity returns have averaged high single digits nominally, but any particular 25-year window can differ substantially. Model a range — 5%, 7%, 9% — and plan against the pessimistic case rather than the optimistic one.
Does this account for market volatility?
No. It applies a constant return, which is the right tool for comparing scenarios and sizing contributions but not for assessing risk. Real sequences matter: poor early returns hurt a contribution plan far less than they hurt a drawdown plan.
Are the contributions assumed at the start or end of the month?
The end, which is the conservative ordinary-annuity convention. Contributing at the start of each month would add roughly one extra month of growth to every contribution, increasing the result by a fraction of a per cent over a long horizon.
Is the result before or after tax?
Before. In a tax-sheltered account the projection is close to what you keep; in a taxable account, dividends and realised gains are taxed along the way, which acts like an additional fee. Model that drag by increasing the fee input.
Should I invest a lump sum or contribute monthly?
If you already hold the cash, investing it immediately has historically beaten averaging it in, because markets rise more often than they fall. Averaging in reduces regret risk rather than expected return. This engine models both components separately.
What is the expense ratio and where do I find it?
It is the annual percentage a fund deducts for management, published in the fund factsheet or key information document. Index trackers commonly charge under 0.20%; active funds frequently exceed 0.75%. Platform and advice fees are additional — add them all into the fee box.
How long until my money doubles?
At a 7.25% net return, 9.59 years. The rule of 72 estimates 9.9 years. Note that this applies to the invested balance, not to a plan with ongoing contributions, where the balance grows for two distinct reasons at once.
Why separate contributions from growth?
Because it shows whether a projection is the market working or simply you saving. Here $160,000 of contributions produced $322,366.60 of growth, so 66.8% of the result is return. Over short horizons that share is far smaller, and the plan is really a savings plan.
Can I model an annual contribution increase?
Not directly — the engine holds the contribution constant. As an approximation, use your average expected contribution across the horizon rather than today's figure, which understates a plan you intend to escalate with income.
Does it matter which account I use?
Substantially. Tax-advantaged accounts remove the tax drag entirely for the whole horizon, which on these numbers is worth more than any plausible fund selection. Fill the sheltered allowances before optimising fund choice.
What if I need to withdraw early?
Then the horizon shortens and the growth share collapses, because compounding does most of its work in the final years. Money needed within five years generally does not belong in a volatile portfolio at all; use the Savings Calculator instead.
Is 3% the right inflation assumption?
It is a reasonable long-run central estimate for developed economies, but your personal inflation rate depends on what you buy. Housing, education and healthcare have run persistently above the headline index. Test 4% before treating a plan as safe.
Why does the fee cost more than the fee rate suggests?
Because 0.75% is charged on the balance, not on the growth. In a year when the portfolio returns 8%, the fee consumes over 9% of that year's gain — and then the lost amount never compounds again for the remaining decades.
Is this investment calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.
Can I use it offline?
Largely, yes. Because computation is client-side, the page continues to calculate without a network connection once it has loaded.