Savings Calculator 2026 — Calculate Compound Interest, FIRE Number & Investment Growth
See exactly how your money grows. Initial deposit, monthly contribution, compound interest — plus a year-by-year growth chart.
📚 Official sources
This calculator solves the standard future-value formula with recurring contributions (annuity). It supports monthly, quarterly and yearly compounding, and lets you pick whether contributions happen at the start or end of each period. Great for emergency-fund planning, FIRE targets, or pension top-ups.
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How to use it
- Pick your currency and the compounding frequency (monthly is the typical bank setting).
- Enter your initial deposit and how much you can save every month.
- Set an expected annual interest rate — historically stock ETFs averaged ~7% real, savings accounts 2-5%.
- Pick the number of years to project. The chart shows balance vs. contributions growing apart as interest compounds.
How is the savings growth calculated?
Every value this calculator returns comes from a single textbook formula: the future value (FV) of money compounded over time. For a one-time lump sum with no further deposits, FV = PV × (1 + r)^n, where PV is the present value (the initial deposit), r is the periodic interest rate (annual rate divided by the compounding frequency) and n is the total number of compounding periods. Compounding means the interest earned in one period is added to the balance and itself earns interest in the next period — that is the mechanism Albert Einstein is loosely credited with calling 'the eighth wonder of the world'.
When you also save a fixed amount on a regular schedule, the formula extends to FV = PV × (1 + r)^n + PMT × ((1 + r)^n − 1) / r. The second term is the future value of an ordinary annuity: a stream of equal payments PMT made at the end of each period. If you select 'Start of period' (an annuity-due) the calculator multiplies that annuity term by an extra (1 + r) to credit interest one period earlier. Internally the engine also runs the simulation period-by-period so the year-by-year chart matches the closed-form total to the cent.
The difference between simple and compound interest grows nonlinearly with time. Simple interest pays r × PV every period and never reinvests it; compound interest reinvests, so the balance follows an exponential curve rather than a straight line. At 5% over 30 years a simple-interest €10,000 deposit grows to €25,000, while the same deposit compounded annually grows to about €43,219. That gap is precisely why the U.S. Securities and Exchange Commission's investor.gov compound-interest calculator stresses starting early: a €100 monthly contribution begun at age 25 ends up worth roughly twice as much at 65 as the same €100/month begun at age 35.
Compounding frequency also matters, although less than people assume. The same 5% nominal rate compounded annually returns 5.000% per year; compounded monthly it returns (1 + 0.05/12)^12 − 1 ≈ 5.116%; compounded daily, about 5.127%. The continuous-compounding limit — calculated as e^r − 1 — is just 5.127% as well. So switching from yearly to monthly is a real but small upgrade; switching from monthly to daily is essentially free precision.
Real return is what actually preserves your purchasing power. If your nominal return is 5% and inflation runs at 3%, the Fisher equation says your real return is approximately (1.05 / 1.03) − 1 ≈ 1.94%, not 2%. The calculator does not subtract inflation automatically: enter the real rate yourself if you want to see today-money growth, or pair it with our inflation calculator. The same goes for tax: in Romania interest income is taxed at 10% under the Codul Fiscal, in Hungary at 15% (kamatadó) plus a 13% szociális hozzájárulási adó on bank deposits since 2023, in Germany at 25% Abgeltungsteuer plus 5.5% Solidaritätszuschlag and possibly church tax, and in Poland the 19% Belka tax. Multiply the headline rate by (1 − tax rate) before entering it for an after-tax projection.
The same engine powers the FIRE (Financial Independence, Retire Early) tab. The 4% safe-withdrawal rate comes from the Trinity Study (Cooley, Hubbard, Walz 1998 and 2009 update), which back-tested rolling 30-year retirement windows on US stock-bond portfolios and found that withdrawing 4% of the starting balance, adjusted yearly for inflation, succeeded over 95% of the time on a 50/50 stock-bond mix. Inverting that gives the FIRE number = annual expenses × 25. Bengen's 2022 work suggests 4.7% may be safer in some regimes; for 40–50 year horizons many planners drop to 3.25–3.5% (so 28–31× expenses). The tab solves PV(1 + r)^n + PMT × ((1 + r)^n − 1) / r = target for n using a closed-form logarithm — exactly the same formula, just rearranged.
Concretely: a €1,000 starting balance plus €200 a month at 5% compounded monthly for 10 years gives €25,000 in contributions and ends at roughly €32,700 — about €7,700 in earned interest. Push the same parameters out to 30 years and the balance reaches roughly €170,000 with €73,000 contributed and €97,000 in interest. That is what the chart visualizes when the 'balance' line pulls away from the 'contributed' line over time. The links in the next section point to the primary academic and regulatory sources for every number quoted here.
💡 Worked example
Initial deposit: €1,000 · Monthly contribution: €200 · Annual rate: 5% (monthly compounding) · Term: 10 years → Final balance ≈ €32,700 = €25,000 contributed + €7,700 earned as interest. FIRE tab: if your monthly spending is €2,000 and the safe withdrawal rate is 4%, your FIRE number is €600,000 (annual expenses × 25).
Frequently Asked Questions
What's the difference between monthly and yearly compounding?
With monthly compounding, the interest accrued each month is added to the balance and itself earns interest next month. Yearly compounding only credits interest once per year. Monthly compounding gives a slightly higher final balance for the same nominal rate.
What does 'contribution timing' mean?
'End of period' (ordinary annuity) is the most common — you save, interest is calculated on the balance before your save. 'Start of period' (annuity-due) adds your contribution before interest, giving a slightly higher final balance.
Does this account for taxes or inflation?
No. Results are gross, in today's money. To model after-tax returns, enter a lower rate (e.g. 5% × (1 − tax rate)). To see inflation-adjusted 'real' purchasing power, enter the real rate (nominal rate − expected inflation).
How accurate is the growth chart?
Exact — the chart is built by simulating period-by-period and the end-of-year snapshots match the closed-form final balance to the cent.
How do I choose a realistic rate of return?
Historical long-term stock market returns are ~7% real (inflation-adjusted) or ~9–10% nominal. Bonds average 2–3% real. Cash/savings ≈ 0% real. Use 5–6% as a conservative balanced portfolio assumption, and always model a worst-case at 3%.
What's the difference between stocks, bonds, and savings accounts for long-term growth?
Stocks offer the highest expected return (7% real) but with large drawdowns (−50% is possible in a single year). Bonds offer steady but lower returns (2–3% real). Savings accounts preserve nominal value but lose 2–3% to inflation yearly. Over 20+ years, stocks dominate — diversified ETFs make them accessible.
When should I use the FIRE tab?
Use it to estimate how much you need saved to retire based on spending, not income. FIRE number = annual expenses × (1 / safe withdrawal rate). The model assumes investments continue growing at a realistic real rate during retirement and that spending doesn't spike.
What's the 4% rule and is it still valid in 2026?
The Trinity Study (1998, updated 2009) found a 4% inflation-adjusted withdrawal rate had a >95% success rate over 30 years with a 50/50 stock-bond portfolio. Some recent research (Bengen 2022) argues 4.7% is safer. For longer horizons (40–50 years) most planners suggest 3.25–3.75%.
Should I invest a lump sum or dollar-cost average?
Vanguard's 2023 study found lump-sum investing beats dollar-cost averaging ~68% of the time over 10 years — markets trend up. But DCA reduces regret risk and is easier behaviorally. If you have a lump sum and a 10+ year horizon, invest it; if you're nervous, spread it over 6–12 months.
How does inflation erode long-term savings?
At 3% inflation, €1,000 today buys only €552 of goods in 20 years — you lose almost half the purchasing power. To preserve real wealth, your after-tax return must exceed inflation. That's why cash under the mattress loses, and why long-term investors need equity exposure.