See what starting early really delivers
An interactive calculator that shows why 20 years of time matters more than 20% higher contributions. Drag the sliders, see the effect instantly — and discover what delaying really costs.
This isn't a guess — this is math
Compound interest is the one thing that lets money genuinely grow for free. Not by working harder, not by earning more — purely through time. Einstein reportedly called it 'the eighth wonder of the world'. We think: it's just the fairest form of rewarding forward-planning.
Below you can set everything yourself: when you start, how much you contribute, what return you expect. Pay special attention to: what happens if you START at 22 versus 32? The difference is usually larger than people expect.
Set your situation
Drag the sliders — the chart updates instantly.
Rules of thumb: savings account ~2%, bonds ~3-4%, equity index ~5-7% (historical average)
Example scenarios
Final amount
€101,322
at age 67
You contributed
€27,000
over 45 years
Earned from interest
€74,322
This comes 'free' from time
Your balance over the years
The light area is your own contribution, the darker area is what interest adds on top.
The price of delay
If you start the same contribution 10 years later, you lose €44,517 from your final balance. That's 10 years of unrecoverable return.
Not from bad luck, not from worse markets — purely because interest had less time to compound on itself.
Three steps: from boring to magical
Compound interest sounds mathematical, but the essence is simple:
You contribute
Every month you set aside an amount. In the first year it's only your own money — nothing exciting.
Interest grows on your balance
After a year your balance earns interest. Small amount — maybe a few dozen euros. Doesn't feel special.
Interest earns interest again
The next year you earn interest on your contribution PLUS on last year's interest. And so on. After 10 years it starts rolling. After 30 years it becomes a snowball.
Honestly — some caveats
This is an ideal scenario. In reality, a few wrinkles apply:
- Returns vary per year. Equities return +20% some years, -15% others. Average ~5-7% long term, but not every year.
- Inflation (~2% per year) erodes purchasing power. €200,000 in 45 years feels like less than €200,000 now.
- Costs: investment fees (ETFs ~0.2-0.5%/year) reduce net return. Savings interest is taxed (box 3).
- This is not financial advice. The calculator is educational — for big decisions: speak to an independent advisor or consult consumer comparison sites.
But: even with all these caveats, the conclusion stands. Starting early is the only factor you fully control — and the one that matters most.
Frequently asked questions
Do I need to invest to get this return?
For 5%+ returns long term: yes, usually. Savings alone typically return 1-3%. But: investing doesn't have to be complicated. A global index fund (ETF) through a Dutch broker (DEGIRO, Meesman, BUX) is enough for most people. No stock-picking, no crypto, no 'hot tips'. For shorter horizon (<10 years) or risk-averse people: savings account or term deposits. Less return but more certainty.
What's a realistic return percentage?
No guarantees possible, but historical averages (EU/US, 1970-2024): • Savings account: 1-3% (recent years often 0-2%) • Government bonds: 2-4% • Global equity index: 5-7% (ignoring inflation) • Stocks + bonds mix (60/40): 4-6% For calculator purposes: 5% is a reasonable middle ground for a global index portfolio. Be careful with numbers >8% — that's optimistic.
Does this apply if I'm already 40+?
Yes, but with different focus. 'The best time to plant a tree was 20 years ago. The second-best time is now.' For 40+: you have 20-25 years until retirement — not 45. So compound interest works less powerfully, but still works. You likely also have higher contribution capacity (higher salary, kids out of house soon, mortgage paid off). Rule of thumb: what you start at 40 can still be 2-3x your total contributions by 65. Not magical like for 20-year-olds, but not nothing.
Is this a recommendation from Okidoky to invest?
No — this is an educational tool. We don't earn money from investing or investment providers. Okidoky is a ledger (household bookkeeping) — not a broker, not an advisor. Why then this calculator? Because our founder has experienced first-hand how a single financial event can shape years of life. Many debt stories could have been avoided if people had earlier insight into how money works long term — or at least had a buffer. This is prevention, not investment advice. For concrete advice: talk to an independent financial advisor.
What's the difference with a mortgage or pension calculator?
This calculator is deliberately simple: one contribution, one return, one timeline. Reality is more complex: • Mortgage: compound interest WORKS AGAINST you (you pay interest on shrinking debt — still significant if mortgage is large) • Pension: tax-deductible (annuity system), indexation, payout rules • Investing in box 3: Dutch wealth tax above ~€57,000 This calculator shows the principle. For specific situations: use specialized calculators (at banks, pension funds, independent advisors).
See where you stand — and what's smart now
This calculator is one puzzle piece. Take our financial health check for a broader picture, or read our guide for young professionals for concrete first steps.